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	$65.31	11.546%	$72.8507	$72.85	$72.85	$72.90
Purchase #2	$39.31	12.649%	$44.2823	$44.28	$44.30	$44.30
Purchase #3	$55.86	12.320%	$62.742	$62.74	$62.75	$62.70
Purchase #4	$11.62	7.272%	$12.465	$12.47	$12.45	$12.50
Purchase #5	$223.51	7.142%	$239.4731	$239.47	$239.45	$239.50
Purchase #6	$149.85	13.538%	$170.1367	$170.14	$170.15	$170.10
Purchase #7	$82.88	8.530%	$89.9497	$89.95	$89.95	$89.90
7 purchase totals =	$628.34		$691.8995	$691.90	$691.90	$691.90