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	$181.48	11.676%	$202.6696	$202.67	$202.65	$202.70
Purchase #2	$173.82	12.855%	$196.1646	$196.16	$196.15	$196.20
Purchase #3	$224.84	13.634%	$255.4947	$255.49	$255.50	$255.50
Purchase #4	$160.38	3.654%	$166.2403	$166.24	$166.25	$166.20
Purchase #5	$110.30	7.822%	$118.9277	$118.93	$118.95	$118.90
Purchase #6	$125.31	6.188%	$133.0642	$133.06	$133.05	$133.10
Purchase #7	$92.48	7.213%	$99.1506	$99.15	$99.15	$99.20
7 purchase totals =	$1,068.61		$1,171.7117	$1,171.70	$1,171.70	$1,171.80