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	$92.85	11.517%	$103.5435	$103.54	$103.55	$103.50
Purchase #2	$101.65	11.677%	$113.5197	$113.52	$113.50	$113.50
Purchase #3	$64.44	3.601%	$66.7605	$66.76	$66.75	$66.80
Purchase #4	$249.36	8.118%	$269.603	$269.60	$269.60	$269.60
Purchase #5	$157.85	13.748%	$179.5512	$179.55	$179.55	$179.60
Purchase #6	$38.31	3.534%	$39.6639	$39.66	$39.65	$39.70
Purchase #7	$158.25	4.646%	$165.6023	$165.60	$165.60	$165.60
7 purchase totals =	$862.71		$938.2441	$938.23	$938.20	$938.30