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	$29.75	10.871%	$32.9841	$32.98	$33.00	$33.00
Purchase #2	$240.65	4.537%	$251.5683	$251.57	$251.55	$251.60
Purchase #3	$159.72	13.108%	$180.6561	$180.66	$180.65	$180.70
Purchase #4	$164.79	3.444%	$170.4654	$170.47	$170.45	$170.50
Purchase #5	$83.40	5.206%	$87.7418	$87.74	$87.75	$87.70
Purchase #6	$209.42	6.256%	$222.5213	$222.52	$222.50	$222.50
Purchase #7	$71.81	6.491%	$76.4712	$76.47	$76.45	$76.50
7 purchase totals =	$959.54		$1,022.4082	$1,022.41	$1,022.35	$1,022.50