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	$46.51	13.534%	$52.8047	$52.80	$52.80	$52.80
Purchase #2	$135.67	3.502%	$140.4212	$140.42	$140.40	$140.40
Purchase #3	$240.48	6.682%	$256.5489	$256.55	$256.55	$256.50
Purchase #4	$62.77	5.849%	$66.4414	$66.44	$66.45	$66.40
Purchase #5	$243.34	5.305%	$256.2492	$256.25	$256.25	$256.20
Purchase #6	$142.89	3.874%	$148.4256	$148.43	$148.45	$148.40
Purchase #7	$104.50	6.829%	$111.6363	$111.64	$111.65	$111.60
7 purchase totals =	$976.16		$1,032.5273	$1,032.53	$1,032.55	$1,032.30