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	$235.53	12.291%	$264.479	$264.48	$264.50	$264.50
Purchase #2	$155.45	3.580%	$161.0151	$161.02	$161.00	$161.00
Purchase #3	$152.37	4.772%	$159.6411	$159.64	$159.65	$159.60
Purchase #4	$33.93	3.418%	$35.0897	$35.09	$35.10	$35.10
Purchase #5	$182.96	9.578%	$200.4839	$200.48	$200.50	$200.50
Purchase #6	$122.31	7.191%	$131.1053	$131.11	$131.10	$131.10
Purchase #7	$230.61	13.780%	$262.3881	$262.39	$262.40	$262.40
7 purchase totals =	$1,113.16		$1,214.2022	$1,214.21	$1,214.25	$1,214.20