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	$55.60	5.329%	$58.5629	$58.56	$58.55	$58.60
Purchase #2	$191.95	13.217%	$217.32	$217.32	$217.30	$217.30
Purchase #3	$205.31	9.145%	$224.0856	$224.09	$224.10	$224.10
Purchase #4	$100.88	10.189%	$111.1587	$111.16	$111.15	$111.20
Purchase #5	$41.54	7.716%	$44.7452	$44.75	$44.75	$44.70
Purchase #6	$38.36	9.340%	$41.9428	$41.94	$41.95	$41.90
Purchase #7	$37.90	7.235%	$40.6421	$40.64	$40.65	$40.60
7 purchase totals =	$671.54		$738.4573	$738.46	$738.45	$738.40