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	$132.82	9.354%	$145.244	$145.24	$145.25	$145.20
Purchase #2	$187.73	5.431%	$197.9256	$197.93	$197.95	$197.90
Purchase #3	$113.43	12.333%	$127.4193	$127.42	$127.40	$127.40
Purchase #4	$227.43	10.111%	$250.4254	$250.43	$250.45	$250.40
Purchase #5	$10.45	10.137%	$11.5093	$11.51	$11.50	$11.50
Purchase #6	$224.74	5.532%	$237.1726	$237.17	$237.15	$237.20
Purchase #7	$212.97	13.103%	$240.8755	$240.88	$240.90	$240.90
7 purchase totals =	$1,109.57		$1,210.5717	$1,210.58	$1,210.60	$1,210.50