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	$42.69	5.764%	$45.1507	$45.15	$45.15	$45.20
Purchase #2	$71.83	3.603%	$74.418	$74.42	$74.40	$74.40
Purchase #3	$64.48	12.779%	$72.7199	$72.72	$72.70	$72.70
Purchase #4	$182.72	11.608%	$203.9301	$203.93	$203.95	$203.90
Purchase #5	$123.25	6.392%	$131.1281	$131.13	$131.15	$131.10
Purchase #6	$210.55	6.160%	$223.5199	$223.52	$223.50	$223.50
Purchase #7	$155.91	6.196%	$165.5702	$165.57	$165.55	$165.60
7 purchase totals =	$851.43		$916.4369	$916.44	$916.40	$916.40