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	$211.49	11.243%	$235.2678	$235.27	$235.25	$235.30
Purchase #2	$33.75	11.198%	$37.5293	$37.53	$37.55	$37.50
Purchase #3	$53.80	12.533%	$60.5428	$60.54	$60.55	$60.50
Purchase #4	$151.91	13.756%	$172.8067	$172.81	$172.80	$172.80
Purchase #5	$189.67	7.237%	$203.3964	$203.40	$203.40	$203.40
Purchase #6	$34.56	8.819%	$37.6078	$37.61	$37.60	$37.60
Purchase #7	$57.26	3.668%	$59.3603	$59.36	$59.35	$59.40
7 purchase totals =	$732.44		$806.5111	$806.52	$806.50	$806.50