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	$151.66	8.188%	$164.0779	$164.08	$164.10	$164.10
Purchase #2	$129.49	7.477%	$139.172	$139.17	$139.15	$139.20
Purchase #3	$110.81	12.126%	$124.2468	$124.25	$124.25	$124.20
Purchase #4	$162.28	3.324%	$167.6742	$167.67	$167.65	$167.70
Purchase #5	$142.58	11.606%	$159.1278	$159.13	$159.15	$159.10
Purchase #6	$246.33	10.766%	$272.8499	$272.85	$272.85	$272.80
Purchase #7	$32.70	3.809%	$33.9455	$33.95	$33.95	$33.90
7 purchase totals =	$975.85		$1,061.0941	$1,061.10	$1,061.10	$1,061.00