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	$217.54	7.341%	$233.5096	$233.51	$233.50	$233.50
Purchase #2	$117.48	12.121%	$131.7198	$131.72	$131.70	$131.70
Purchase #3	$204.61	11.833%	$228.8215	$228.82	$228.80	$228.80
Purchase #4	$158.33	13.458%	$179.6381	$179.64	$179.65	$179.60
Purchase #5	$200.75	13.362%	$227.5742	$227.57	$227.55	$227.60
Purchase #6	$159.44	3.822%	$165.5338	$165.53	$165.55	$165.50
Purchase #7	$93.75	11.640%	$104.6625	$104.66	$104.65	$104.70
7 purchase totals =	$1,151.90		$1,271.4595	$1,271.45	$1,271.40	$1,271.40