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	$166.56	3.693%	$172.7111	$172.71	$172.70	$172.70
Purchase #2	$34.89	4.635%	$36.5072	$36.51	$36.50	$36.50
Purchase #3	$146.25	4.167%	$152.3442	$152.34	$152.35	$152.30
Purchase #4	$106.43	4.610%	$111.3364	$111.34	$111.35	$111.30
Purchase #5	$145.93	8.334%	$158.0918	$158.09	$158.10	$158.10
Purchase #6	$149.85	3.463%	$155.0393	$155.04	$155.05	$155.00
Purchase #7	$110.73	5.400%	$116.7094	$116.71	$116.70	$116.70
7 purchase totals =	$860.64		$902.7394	$902.74	$902.75	$902.60