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	$154.34	13.691%	$175.4707	$175.47	$175.45	$175.50
Purchase #2	$225.50	12.383%	$253.4237	$253.42	$253.40	$253.40
Purchase #3	$45.79	10.294%	$50.5036	$50.50	$50.50	$50.50
Purchase #4	$210.52	12.854%	$237.5802	$237.58	$237.60	$237.60
Purchase #5	$243.57	11.339%	$271.1884	$271.19	$271.20	$271.20
Purchase #6	$157.64	4.707%	$165.0601	$165.06	$165.05	$165.10
Purchase #7	$98.27	13.591%	$111.6259	$111.63	$111.65	$111.60
7 purchase totals =	$1,135.63		$1,264.8526	$1,264.85	$1,264.85	$1,264.90