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	$111.98	12.241%	$125.6875	$125.69	$125.70	$125.70
Purchase #2	$10.33	5.636%	$10.9122	$10.91	$10.90	$10.90
Purchase #3	$78.49	13.544%	$89.1207	$89.12	$89.10	$89.10
Purchase #4	$107.84	13.793%	$122.7144	$122.71	$122.70	$122.70
Purchase #5	$123.83	13.483%	$140.526	$140.53	$140.55	$140.50
Purchase #6	$77.71	7.400%	$83.4605	$83.46	$83.45	$83.50
Purchase #7	$126.69	10.276%	$139.7087	$139.71	$139.70	$139.70
7 purchase totals =	$636.87		$712.1300	$712.13	$712.10	$712.10