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	$38.85	5.304%	$40.9106	$40.91	$40.90	$40.90
Purchase #2	$48.65	13.525%	$55.2299	$55.23	$55.25	$55.20
Purchase #3	$244.79	4.503%	$255.8129	$255.81	$255.80	$255.80
Purchase #4	$116.67	6.596%	$124.3656	$124.37	$124.35	$124.40
Purchase #5	$217.80	11.867%	$243.6463	$243.65	$243.65	$243.60
Purchase #6	$241.84	6.123%	$256.6479	$256.65	$256.65	$256.60
Purchase #7	$192.80	8.458%	$209.107	$209.11	$209.10	$209.10
7 purchase totals =	$1,101.40		$1,185.7202	$1,185.73	$1,185.70	$1,185.60