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	$219.74	13.850%	$250.174	$250.17	$250.15	$250.20
Purchase #2	$247.34	11.572%	$275.9622	$275.96	$275.95	$276.00
Purchase #3	$154.68	11.770%	$172.8858	$172.89	$172.90	$172.90
Purchase #4	$122.39	13.765%	$139.237	$139.24	$139.25	$139.20
Purchase #5	$100.53	6.139%	$106.7015	$106.70	$106.70	$106.70
Purchase #6	$139.66	11.291%	$155.429	$155.43	$155.45	$155.40
Purchase #7	$78.41	13.422%	$88.9342	$88.93	$88.95	$88.90
7 purchase totals =	$1,062.75		$1,189.3237	$1,189.32	$1,189.35	$1,189.30