Currently the position of ticks and thereby of the grid lines are calculated starting from the minimum of the axis. For example, if you set chart:minimum="-2.5" and chart:interval-major="2" you get ticks at -2.5, -0.5, 1.5, 3.5. But you likely want to get ticks at -2, 0, 2, 4. The situation is worth, when you use logarithmic scaling. Here you need a lot of mathematic for to get e.g. the ticks at 100, 200, 400, 800, 1600 and an axis start somewhere between 50 and 100. Gnumeric has no special setting, but uses 0 as position for linear axes and 1 as position for logarithmic axes. That does not mean, that these values need to be included in the actual interval of the axis. Excel has no special setting, but starts at minimum too. I propose to introduce an attribute chart:tick-marks-ref-value, with values "start", "end" or any double value. The major ticks are then positioned in a way, that one major tick is on this position. The given double value need not be inside the chart:minimum - chart:maximum range, but determines the entire grid. The values "start" and "end" are needed to get the current behavior, especially when auto-scaling is on. Having such attribute would ease the use of Calc for scientific and educational use cases.
Setting to NEW.. for science!
ODF will be extended (see URL) with attributes chart:major-origin attribute and chart:minor-logarithmic, likely in ODF 1.4. When implementing such feature, consider the new ODF attributes.