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	$60.75	11.631%	$67.8158	$67.82	$67.80	$67.80
Purchase #2	$11.46	4.155%	$11.9362	$11.94	$11.95	$11.90
Purchase #3	$80.38	12.539%	$90.4588	$90.46	$90.45	$90.50
Purchase #4	$28.37	13.219%	$32.1202	$32.12	$32.10	$32.10
Purchase #5	$66.84	12.628%	$75.2806	$75.28	$75.30	$75.30
Purchase #6	$208.80	7.785%	$225.0551	$225.06	$225.05	$225.10
Purchase #7	$11.89	7.223%	$12.7488	$12.75	$12.75	$12.70
7 purchase totals =	$468.49		$515.4155	$515.43	$515.40	$515.40