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	$223.58	13.530%	$253.8304	$253.83	$253.85	$253.80
Purchase #2	$243.31	5.148%	$255.8356	$255.84	$255.85	$255.80
Purchase #3	$52.44	6.738%	$55.9734	$55.97	$55.95	$56.00
Purchase #4	$35.99	5.110%	$37.8291	$37.83	$37.85	$37.80
Purchase #5	$11.69	4.130%	$12.1728	$12.17	$12.15	$12.20
Purchase #6	$56.50	6.576%	$60.2154	$60.22	$60.20	$60.20
Purchase #7	$159.71	11.759%	$178.4903	$178.49	$178.50	$178.50
7 purchase totals =	$783.22		$854.3470	$854.35	$854.35	$854.30