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	$206.56	11.416%	$230.1409	$230.14	$230.15	$230.10
Purchase #2	$106.70	8.430%	$115.6948	$115.69	$115.70	$115.70
Purchase #3	$134.95	4.404%	$140.8932	$140.89	$140.90	$140.90
Purchase #4	$36.56	11.516%	$40.7702	$40.77	$40.75	$40.80
Purchase #5	$176.33	13.605%	$200.3197	$200.32	$200.30	$200.30
Purchase #6	$29.62	10.165%	$32.6309	$32.63	$32.65	$32.60
Purchase #7	$103.59	7.643%	$111.5074	$111.51	$111.50	$111.50
7 purchase totals =	$794.31		$871.9571	$871.95	$871.95	$871.90