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	$151.67	13.691%	$172.4351	$172.44	$172.45	$172.40
Purchase #2	$222.86	12.576%	$250.8869	$250.89	$250.90	$250.90
Purchase #3	$213.75	4.469%	$223.3025	$223.30	$223.30	$223.30
Purchase #4	$241.91	10.468%	$267.2331	$267.23	$267.25	$267.20
Purchase #5	$245.98	13.537%	$279.2783	$279.28	$279.30	$279.30
Purchase #6	$192.59	8.857%	$209.6477	$209.65	$209.65	$209.60
Purchase #7	$140.27	13.503%	$159.2107	$159.21	$159.20	$159.20
7 purchase totals =	$1,409.03		$1,561.9943	$1,562.00	$1,562.05	$1,561.90