Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$61.86	7.602%	$66.5626	$66.56	$66.55	$66.60
Purchase #2	$149.91	3.691%	$155.4432	$155.44	$155.45	$155.40
Purchase #3	$59.64	11.105%	$66.263	$66.26	$66.25	$66.30
Purchase #4	$26.72	3.756%	$27.7236	$27.72	$27.70	$27.70
Purchase #5	$140.44	12.614%	$158.1551	$158.16	$158.15	$158.20
Purchase #6	$247.63	4.854%	$259.65	$259.65	$259.65	$259.70
Purchase #7	$57.53	6.694%	$61.3811	$61.38	$61.40	$61.40
7 purchase totals =	$743.73		$795.1786	$795.17	$795.15	$795.30