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	$144.66	4.518%	$151.1957	$151.20	$151.20	$151.20
Purchase #2	$75.95	12.453%	$85.4081	$85.41	$85.40	$85.40
Purchase #3	$18.98	9.551%	$20.7928	$20.79	$20.80	$20.80
Purchase #4	$157.29	6.443%	$167.4242	$167.42	$167.40	$167.40
Purchase #5	$10.48	5.124%	$11.017	$11.02	$11.00	$11.00
Purchase #6	$122.34	6.537%	$130.3374	$130.34	$130.35	$130.30
Purchase #7	$38.53	9.607%	$42.2316	$42.23	$42.25	$42.20
7 purchase totals =	$568.23		$608.4068	$608.41	$608.40	$608.30