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	$137.28	10.176%	$151.2496	$151.25	$151.25	$151.20
Purchase #2	$45.71	12.866%	$51.591	$51.59	$51.60	$51.60
Purchase #3	$151.74	11.715%	$169.5163	$169.52	$169.50	$169.50
Purchase #4	$237.29	5.387%	$250.0728	$250.07	$250.05	$250.10
Purchase #5	$150.40	5.234%	$158.2719	$158.27	$158.25	$158.30
Purchase #6	$139.42	8.332%	$151.0365	$151.04	$151.05	$151.00
Purchase #7	$13.70	3.143%	$14.1306	$14.13	$14.15	$14.10
7 purchase totals =	$875.54		$945.8687	$945.87	$945.85	$945.80