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	$146.70	11.873%	$164.1177	$164.12	$164.10	$164.10
Purchase #2	$76.88	11.700%	$85.875	$85.88	$85.90	$85.90
Purchase #3	$43.90	13.210%	$49.6992	$49.70	$49.70	$49.70
Purchase #4	$109.77	3.244%	$113.3309	$113.33	$113.35	$113.30
Purchase #5	$199.67	4.422%	$208.4994	$208.50	$208.50	$208.50
Purchase #6	$195.47	7.403%	$209.9406	$209.94	$209.95	$209.90
Purchase #7	$132.80	3.545%	$137.5078	$137.51	$137.50	$137.50
7 purchase totals =	$905.19		$968.9706	$968.98	$969.00	$968.90