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	$34.86	4.757%	$36.5183	$36.52	$36.50	$36.50
Purchase #2	$41.44	10.873%	$45.9458	$45.95	$45.95	$45.90
Purchase #3	$56.50	13.385%	$64.0625	$64.06	$64.05	$64.10
Purchase #4	$5.67	11.529%	$6.3237	$6.32	$6.30	$6.30
Purchase #5	$37.74	9.316%	$41.2559	$41.26	$41.25	$41.30
Purchase #6	$66.78	7.191%	$71.5821	$71.58	$71.60	$71.60
Purchase #7	$44.81	13.551%	$50.8822	$50.88	$50.90	$50.90
7 purchase totals =	$287.80		$316.5705	$316.57	$316.55	$316.60