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	$11.30	9.809%	$12.4084	$12.41	$12.40	$12.40
Purchase #2	$119.85	8.680%	$130.253	$130.25	$130.25	$130.30
Purchase #3	$139.63	4.485%	$145.8924	$145.89	$145.90	$145.90
Purchase #4	$159.90	6.261%	$169.9113	$169.91	$169.90	$169.90
Purchase #5	$188.35	9.453%	$206.1547	$206.15	$206.15	$206.20
Purchase #6	$180.58	5.647%	$190.7774	$190.78	$190.80	$190.80
Purchase #7	$30.71	4.344%	$32.044	$32.04	$32.05	$32.00
7 purchase totals =	$830.32		$887.4412	$887.43	$887.45	$887.50