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	13.696%	$88.3418	$88.34	$88.35	$88.30
Purchase #2	$10.31	9.820%	$11.3224	$11.32	$11.30	$11.30
Purchase #3	$84.83	8.723%	$92.2297	$92.23	$92.25	$92.20
Purchase #4	$29.95	5.174%	$31.4996	$31.50	$31.50	$31.50
Purchase #5	$13.27	6.553%	$14.1396	$14.14	$14.15	$14.10
Purchase #6	$144.56	11.422%	$161.0716	$161.07	$161.05	$161.10
Purchase #7	$85.77	4.310%	$89.4667	$89.47	$89.45	$89.50
7 purchase totals =	$446.39		$488.0714	$488.07	$488.05	$488.00