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	$60.67	11.240%	$67.4893	$67.49	$67.50	$67.50
Purchase #2	$55.83	11.489%	$62.2443	$62.24	$62.25	$62.20
Purchase #3	$122.60	10.557%	$135.5429	$135.54	$135.55	$135.50
Purchase #4	$87.43	12.272%	$98.1594	$98.16	$98.15	$98.20
Purchase #5	$48.58	11.459%	$54.1468	$54.15	$54.15	$54.10
Purchase #6	$222.76	11.403%	$248.1613	$248.16	$248.15	$248.20
Purchase #7	$222.42	7.233%	$238.5076	$238.51	$238.50	$238.50
7 purchase totals =	$820.29		$904.2516	$904.25	$904.25	$904.20