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	$154.61	12.205%	$173.4802	$173.48	$173.50	$173.50
Purchase #2	$245.60	11.733%	$274.4162	$274.42	$274.40	$274.40
Purchase #3	$39.86	11.874%	$44.593	$44.59	$44.60	$44.60
Purchase #4	$227.90	11.475%	$254.0515	$254.05	$254.05	$254.10
Purchase #5	$247.57	3.611%	$256.5098	$256.51	$256.50	$256.50
Purchase #6	$146.71	9.424%	$160.536	$160.54	$160.55	$160.50
Purchase #7	$95.47	5.782%	$100.9901	$100.99	$101.00	$101.00
7 purchase totals =	$1,157.72		$1,264.5768	$1,264.58	$1,264.60	$1,264.60