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	$46.98	12.811%	$52.9986	$53.00	$53.00	$53.00
Purchase #2	$195.73	13.364%	$221.8874	$221.89	$221.90	$221.90
Purchase #3	$135.76	3.562%	$140.5958	$140.60	$140.60	$140.60
Purchase #4	$146.39	3.166%	$151.0247	$151.02	$151.00	$151.00
Purchase #5	$45.33	12.388%	$50.9455	$50.95	$50.95	$50.90
Purchase #6	$42.42	11.196%	$47.1693	$47.17	$47.15	$47.20
Purchase #7	$49.69	7.188%	$53.2617	$53.26	$53.25	$53.30
7 purchase totals =	$662.30		$717.8830	$717.89	$717.85	$717.90