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	$75.78	12.850%	$85.5177	$85.52	$85.50	$85.50
Purchase #2	$151.59	5.360%	$159.7152	$159.72	$159.70	$159.70
Purchase #3	$78.73	5.626%	$83.1593	$83.16	$83.15	$83.20
Purchase #4	$14.88	4.666%	$15.5743	$15.57	$15.55	$15.60
Purchase #5	$44.39	4.210%	$46.2588	$46.26	$46.25	$46.30
Purchase #6	$95.45	3.766%	$99.0446	$99.04	$99.05	$99.00
Purchase #7	$235.74	10.793%	$261.1834	$261.18	$261.20	$261.20
7 purchase totals =	$696.56		$750.4533	$750.45	$750.40	$750.50