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	$216.58	12.394%	$243.4229	$243.42	$243.40	$243.40
Purchase #2	$188.73	10.642%	$208.8146	$208.81	$208.80	$208.80
Purchase #3	$158.91	3.267%	$164.1016	$164.10	$164.10	$164.10
Purchase #4	$83.51	4.650%	$87.3932	$87.39	$87.40	$87.40
Purchase #5	$158.30	11.743%	$176.8892	$176.89	$176.90	$176.90
Purchase #6	$11.51	3.312%	$11.8912	$11.89	$11.90	$11.90
Purchase #7	$50.66	7.485%	$54.4519	$54.45	$54.45	$54.50
7 purchase totals =	$868.20		$946.9646	$946.95	$946.95	$947.00