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	$54.80	13.780%	$62.3514	$62.35	$62.35	$62.40
Purchase #2	$215.92	6.589%	$230.147	$230.15	$230.15	$230.10
Purchase #3	$37.49	7.849%	$40.4326	$40.43	$40.45	$40.40
Purchase #4	$64.51	10.794%	$71.4732	$71.47	$71.45	$71.50
Purchase #5	$154.70	9.304%	$169.0933	$169.09	$169.10	$169.10
Purchase #6	$244.61	10.171%	$269.4893	$269.49	$269.50	$269.50
Purchase #7	$141.91	8.263%	$153.636	$153.64	$153.65	$153.60
7 purchase totals =	$913.94		$996.6228	$996.62	$996.65	$996.60