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	$224.41	11.673%	$250.6054	$250.61	$250.60	$250.60
Purchase #2	$128.51	4.742%	$134.6039	$134.60	$134.60	$134.60
Purchase #3	$84.86	5.733%	$89.725	$89.73	$89.75	$89.70
Purchase #4	$53.25	13.555%	$60.468	$60.47	$60.45	$60.50
Purchase #5	$32.95	3.317%	$34.043	$34.04	$34.05	$34.00
Purchase #6	$49.87	9.477%	$54.5962	$54.60	$54.60	$54.60
Purchase #7	$216.73	4.823%	$227.1829	$227.18	$227.20	$227.20
7 purchase totals =	$790.58		$851.2244	$851.23	$851.25	$851.20