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	$127.92	11.480%	$142.6052	$142.61	$142.60	$142.60
Purchase #2	$222.96	6.733%	$237.9719	$237.97	$237.95	$238.00
Purchase #3	$90.72	9.461%	$99.303	$99.30	$99.30	$99.30
Purchase #4	$204.59	13.545%	$232.3017	$232.30	$232.30	$232.30
Purchase #5	$153.35	12.193%	$172.048	$172.05	$172.05	$172.00
Purchase #6	$111.30	10.652%	$123.1557	$123.16	$123.15	$123.20
Purchase #7	$130.76	3.354%	$135.1457	$135.15	$135.15	$135.10
7 purchase totals =	$1,041.60		$1,142.5312	$1,142.54	$1,142.50	$1,142.50