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	$222.96	13.738%	$253.5902	$253.59	$253.60	$253.60
Purchase #2	$37.71	13.262%	$42.7111	$42.71	$42.70	$42.70
Purchase #3	$85.96	11.634%	$95.9606	$95.96	$95.95	$96.00
Purchase #4	$11.50	4.326%	$11.9975	$12.00	$12.00	$12.00
Purchase #5	$30.40	3.785%	$31.5506	$31.55	$31.55	$31.60
Purchase #6	$176.99	10.681%	$195.8943	$195.89	$195.90	$195.90
Purchase #7	$173.71	9.457%	$190.1378	$190.14	$190.15	$190.10
7 purchase totals =	$739.23		$821.8421	$821.84	$821.85	$821.90