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	$227.49	11.413%	$253.4534	$253.45	$253.45	$253.50
Purchase #2	$46.34	9.110%	$50.5616	$50.56	$50.55	$50.60
Purchase #3	$29.90	11.472%	$33.3301	$33.33	$33.35	$33.30
Purchase #4	$218.35	7.699%	$235.1608	$235.16	$235.15	$235.20
Purchase #5	$10.27	4.652%	$10.7478	$10.75	$10.75	$10.70
Purchase #6	$96.44	3.590%	$99.9022	$99.90	$99.90	$99.90
Purchase #7	$29.28	9.797%	$32.1486	$32.15	$32.15	$32.10
7 purchase totals =	$658.07		$715.3045	$715.30	$715.30	$715.30