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	$30.96	5.847%	$32.7702	$32.77	$32.75	$32.80
Purchase #2	$123.43	3.287%	$127.4871	$127.49	$127.50	$127.50
Purchase #3	$6.80	10.263%	$7.4979	$7.50	$7.50	$7.50
Purchase #4	$41.68	6.178%	$44.255	$44.26	$44.25	$44.30
Purchase #5	$88.32	7.198%	$94.6773	$94.68	$94.70	$94.70
Purchase #6	$98.52	11.286%	$109.639	$109.64	$109.65	$109.60
Purchase #7	$55.60	7.631%	$59.8428	$59.84	$59.85	$59.80
7 purchase totals =	$445.31		$476.1693	$476.18	$476.20	$476.20