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	$106.54	4.628%	$111.4707	$111.47	$111.45	$111.50
Purchase #2	$238.74	4.178%	$248.7146	$248.71	$248.70	$248.70
Purchase #3	$208.70	7.117%	$223.5532	$223.55	$223.55	$223.60
Purchase #4	$227.43	11.180%	$252.8567	$252.86	$252.85	$252.90
Purchase #5	$206.43	13.258%	$233.7985	$233.80	$233.80	$233.80
Purchase #6	$52.77	8.222%	$57.1087	$57.11	$57.10	$57.10
Purchase #7	$91.37	3.624%	$94.6812	$94.68	$94.70	$94.70
7 purchase totals =	$1,131.98		$1,222.1836	$1,222.18	$1,222.15	$1,222.30