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	$136.98	9.756%	$150.3438	$150.34	$150.35	$150.30
Purchase #2	$250.96	10.468%	$277.2305	$277.23	$277.25	$277.20
Purchase #3	$171.67	4.663%	$179.675	$179.68	$179.70	$179.70
Purchase #4	$109.48	7.395%	$117.576	$117.58	$117.60	$117.60
Purchase #5	$56.31	13.388%	$63.8488	$63.85	$63.85	$63.80
Purchase #6	$98.38	13.648%	$111.8069	$111.81	$111.80	$111.80
Purchase #7	$33.38	4.661%	$34.9358	$34.94	$34.95	$34.90
7 purchase totals =	$857.16		$935.4168	$935.43	$935.50	$935.30