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	$175.67	8.806%	$191.1395	$191.14	$191.15	$191.10
Purchase #2	$116.63	11.661%	$130.2302	$130.23	$130.25	$130.20
Purchase #3	$198.59	13.708%	$225.8127	$225.81	$225.80	$225.80
Purchase #4	$32.41	6.672%	$34.5724	$34.57	$34.55	$34.60
Purchase #5	$165.76	4.491%	$173.2043	$173.20	$173.20	$173.20
Purchase #6	$221.89	3.862%	$230.4594	$230.46	$230.45	$230.50
Purchase #7	$181.48	3.539%	$187.9026	$187.90	$187.90	$187.90
7 purchase totals =	$1,092.43		$1,173.3211	$1,173.31	$1,173.30	$1,173.30