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	$118.72	6.230%	$126.1163	$126.12	$126.10	$126.10
Purchase #2	$121.66	9.763%	$133.5377	$133.54	$133.55	$133.50
Purchase #3	$126.73	13.801%	$144.22	$144.22	$144.20	$144.20
Purchase #4	$140.94	12.604%	$158.7041	$158.70	$158.70	$158.70
Purchase #5	$141.41	6.768%	$150.9806	$150.98	$151.00	$151.00
Purchase #6	$54.35	12.619%	$61.2084	$61.21	$61.20	$61.20
Purchase #7	$168.69	11.539%	$188.1551	$188.16	$188.15	$188.20
7 purchase totals =	$872.50		$962.9222	$962.93	$962.90	$962.90