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	$151.87	13.846%	$172.8979	$172.90	$172.90	$172.90
Purchase #2	$17.48	3.842%	$18.1516	$18.15	$18.15	$18.20
Purchase #3	$225.64	12.810%	$254.5445	$254.54	$254.55	$254.50
Purchase #4	$62.69	6.166%	$66.5555	$66.56	$66.55	$66.60
Purchase #5	$83.43	12.733%	$94.0531	$94.05	$94.05	$94.10
Purchase #6	$162.99	5.410%	$171.8078	$171.81	$171.80	$171.80
Purchase #7	$140.83	10.785%	$156.0185	$156.02	$156.00	$156.00
7 purchase totals =	$844.93		$934.0289	$934.03	$934.00	$934.10