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	$77.70	5.852%	$82.247	$82.25	$82.25	$82.20
Purchase #2	$161.52	4.449%	$168.706	$168.71	$168.70	$168.70
Purchase #3	$6.43	13.563%	$7.3021	$7.30	$7.30	$7.30
Purchase #4	$155.44	8.833%	$169.17	$169.17	$169.15	$169.20
Purchase #5	$151.85	9.293%	$165.9614	$165.96	$165.95	$166.00
Purchase #6	$69.30	10.105%	$76.3028	$76.30	$76.30	$76.30
Purchase #7	$13.96	13.293%	$15.8157	$15.82	$15.80	$15.80
7 purchase totals =	$636.20		$685.5050	$685.51	$685.45	$685.50