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	$132.25	8.384%	$143.3378	$143.34	$143.35	$143.30
Purchase #2	$235.32	8.462%	$255.2328	$255.23	$255.25	$255.20
Purchase #3	$18.39	10.631%	$20.345	$20.35	$20.35	$20.30
Purchase #4	$36.65	10.802%	$40.6089	$40.61	$40.60	$40.60
Purchase #5	$130.38	5.159%	$137.1063	$137.11	$137.10	$137.10
Purchase #6	$140.60	12.369%	$157.9908	$157.99	$158.00	$158.00
Purchase #7	$237.50	11.678%	$265.2353	$265.24	$265.25	$265.20
7 purchase totals =	$931.09		$1,019.8569	$1,019.87	$1,019.90	$1,019.70