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	$40.52	12.197%	$45.4622	$45.46	$45.45	$45.50
Purchase #2	$210.28	6.363%	$223.6601	$223.66	$223.65	$223.70
Purchase #3	$151.60	8.802%	$164.9438	$164.94	$164.95	$164.90
Purchase #4	$177.40	10.210%	$195.5125	$195.51	$195.50	$195.50
Purchase #5	$11.87	8.665%	$12.8985	$12.90	$12.90	$12.90
Purchase #6	$21.32	10.812%	$23.6251	$23.63	$23.65	$23.60
Purchase #7	$197.90	5.680%	$209.1407	$209.14	$209.15	$209.10
7 purchase totals =	$810.89		$875.2429	$875.24	$875.25	$875.20