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	$173.70	9.453%	$190.1199	$190.12	$190.10	$190.10
Purchase #2	$45.58	10.419%	$50.329	$50.33	$50.35	$50.30
Purchase #3	$9.89	4.218%	$10.3072	$10.31	$10.30	$10.30
Purchase #4	$194.92	4.366%	$203.4302	$203.43	$203.45	$203.40
Purchase #5	$241.51	6.393%	$256.9497	$256.95	$256.95	$256.90
Purchase #6	$40.30	4.179%	$41.9841	$41.98	$42.00	$42.00
Purchase #7	$47.89	10.709%	$53.0185	$53.02	$53.00	$53.00
7 purchase totals =	$753.79		$806.1386	$806.14	$806.15	$806.00