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	$220.80	11.461%	$246.1059	$246.11	$246.10	$246.10
Purchase #2	$61.50	4.437%	$64.2288	$64.23	$64.25	$64.20
Purchase #3	$76.53	8.338%	$82.9111	$82.91	$82.90	$82.90
Purchase #4	$130.32	12.428%	$146.5162	$146.52	$146.50	$146.50
Purchase #5	$241.31	6.444%	$256.86	$256.86	$256.85	$256.90
Purchase #6	$226.47	12.652%	$255.123	$255.12	$255.10	$255.10
Purchase #7	$19.44	3.346%	$20.0905	$20.09	$20.10	$20.10
7 purchase totals =	$976.37		$1,071.8355	$1,071.84	$1,071.80	$1,071.80