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	$85.63	8.795%	$93.1612	$93.16	$93.15	$93.20
Purchase #2	$33.98	12.723%	$38.3033	$38.30	$38.30	$38.30
Purchase #3	$221.82	8.375%	$240.3974	$240.40	$240.40	$240.40
Purchase #4	$98.53	12.233%	$110.5832	$110.58	$110.60	$110.60
Purchase #5	$12.27	7.147%	$13.1469	$13.15	$13.15	$13.10
Purchase #6	$105.69	5.563%	$111.5695	$111.57	$111.55	$111.60
Purchase #7	$141.32	9.166%	$154.2734	$154.27	$154.25	$154.30
7 purchase totals =	$699.24		$761.4349	$761.43	$761.40	$761.50