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	$40.37	13.255%	$45.721	$45.72	$45.70	$45.70
Purchase #2	$235.51	11.108%	$261.6705	$261.67	$261.65	$261.70
Purchase #3	$101.75	9.805%	$111.7266	$111.73	$111.75	$111.70
Purchase #4	$60.88	7.244%	$65.2901	$65.29	$65.30	$65.30
Purchase #5	$204.53	4.368%	$213.4639	$213.46	$213.45	$213.50
Purchase #6	$38.27	6.172%	$40.632	$40.63	$40.65	$40.60
Purchase #7	$173.89	10.799%	$192.6684	$192.67	$192.65	$192.70
7 purchase totals =	$855.20		$931.1725	$931.17	$931.15	$931.20