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	$33.31	10.430%	$36.7842	$36.78	$36.80	$36.80
Purchase #2	$231.84	7.406%	$249.0101	$249.01	$249.00	$249.00
Purchase #3	$179.80	9.326%	$196.5681	$196.57	$196.55	$196.60
Purchase #4	$229.83	7.706%	$247.5407	$247.54	$247.55	$247.50
Purchase #5	$208.59	6.200%	$221.5226	$221.52	$221.50	$221.50
Purchase #6	$138.98	5.594%	$146.7545	$146.75	$146.75	$146.80
Purchase #7	$47.59	6.518%	$50.6919	$50.69	$50.70	$50.70
7 purchase totals =	$1,069.94		$1,148.8721	$1,148.86	$1,148.85	$1,148.90