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	$211.51	6.648%	$225.5712	$225.57	$225.55	$225.60
Purchase #2	$143.59	8.291%	$155.495	$155.50	$155.50	$155.50
Purchase #3	$146.33	3.419%	$151.333	$151.33	$151.35	$151.30
Purchase #4	$34.39	8.531%	$37.3238	$37.32	$37.30	$37.30
Purchase #5	$10.60	11.802%	$11.851	$11.85	$11.85	$11.90
Purchase #6	$39.28	12.760%	$44.2921	$44.29	$44.30	$44.30
Purchase #7	$60.64	8.297%	$65.6713	$65.67	$65.65	$65.70
7 purchase totals =	$646.34		$691.5374	$691.53	$691.50	$691.60