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	$95.50	3.682%	$99.0163	$99.02	$99.00	$99.00
Purchase #2	$122.70	3.754%	$127.3062	$127.31	$127.30	$127.30
Purchase #3	$149.25	11.835%	$166.9137	$166.91	$166.90	$166.90
Purchase #4	$33.66	12.342%	$37.8143	$37.81	$37.80	$37.80
Purchase #5	$43.84	8.378%	$47.5129	$47.51	$47.50	$47.50
Purchase #6	$146.96	7.623%	$158.1628	$158.16	$158.15	$158.20
Purchase #7	$65.94	12.508%	$74.1878	$74.19	$74.20	$74.20
7 purchase totals =	$657.85		$710.9140	$710.91	$710.85	$710.90