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	$121.31	4.610%	$126.9024	$126.90	$126.90	$126.90
Purchase #2	$60.72	8.722%	$66.016	$66.02	$66.00	$66.00
Purchase #3	$40.69	7.859%	$43.8878	$43.89	$43.90	$43.90
Purchase #4	$52.90	9.814%	$58.0916	$58.09	$58.10	$58.10
Purchase #5	$152.43	9.218%	$166.481	$166.48	$166.50	$166.50
Purchase #6	$44.62	12.855%	$50.3559	$50.36	$50.35	$50.40
Purchase #7	$98.79	13.138%	$111.769	$111.77	$111.75	$111.80
7 purchase totals =	$571.46		$623.5037	$623.51	$623.50	$623.60