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	$202.39	12.484%	$227.6564	$227.66	$227.65	$227.70
Purchase #2	$89.61	6.667%	$95.5843	$95.58	$95.60	$95.60
Purchase #3	$56.63	10.219%	$62.417	$62.42	$62.40	$62.40
Purchase #4	$90.50	11.173%	$100.6116	$100.61	$100.60	$100.60
Purchase #5	$146.51	3.568%	$151.7375	$151.74	$151.75	$151.70
Purchase #6	$235.92	4.862%	$247.3904	$247.39	$247.40	$247.40
Purchase #7	$133.98	11.783%	$149.7669	$149.77	$149.75	$149.80
7 purchase totals =	$955.54		$1,035.1641	$1,035.17	$1,035.15	$1,035.20