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	$175.43	7.867%	$189.2311	$189.23	$189.25	$189.20
Purchase #2	$29.67	13.397%	$33.6449	$33.64	$33.65	$33.60
Purchase #3	$225.52	7.733%	$242.9595	$242.96	$242.95	$243.00
Purchase #4	$98.76	13.231%	$111.8269	$111.83	$111.85	$111.80
Purchase #5	$208.38	6.598%	$222.1289	$222.13	$222.15	$222.10
Purchase #6	$13.60	13.328%	$15.4126	$15.41	$15.40	$15.40
Purchase #7	$88.51	3.708%	$91.792	$91.79	$91.80	$91.80
7 purchase totals =	$839.87		$906.9959	$906.99	$907.05	$906.90