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	$200.93	12.691%	$226.43	$226.43	$226.45	$226.40
Purchase #2	$233.75	13.580%	$265.4933	$265.49	$265.50	$265.50
Purchase #3	$82.32	8.846%	$89.602	$89.60	$89.60	$89.60
Purchase #4	$96.81	13.733%	$110.1049	$110.10	$110.10	$110.10
Purchase #5	$139.80	4.588%	$146.214	$146.21	$146.20	$146.20
Purchase #6	$76.66	11.417%	$85.4123	$85.41	$85.40	$85.40
Purchase #7	$152.29	11.804%	$170.2663	$170.27	$170.25	$170.30
7 purchase totals =	$982.56		$1,093.5228	$1,093.51	$1,093.50	$1,093.50