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	$90.68	5.362%	$95.5423	$95.54	$95.55	$95.50
Purchase #2	$250.72	11.472%	$279.4826	$279.48	$279.50	$279.50
Purchase #3	$77.53	7.561%	$83.392	$83.39	$83.40	$83.40
Purchase #4	$148.50	3.582%	$153.8193	$153.82	$153.80	$153.80
Purchase #5	$228.30	12.453%	$256.7302	$256.73	$256.75	$256.70
Purchase #6	$12.70	11.846%	$14.2044	$14.20	$14.20	$14.20
Purchase #7	$158.42	9.399%	$173.3099	$173.31	$173.30	$173.30
7 purchase totals =	$966.85		$1,056.4807	$1,056.47	$1,056.50	$1,056.40