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	$120.30	9.619%	$131.8717	$131.87	$131.85	$131.90
Purchase #2	$196.44	13.785%	$223.5193	$223.52	$223.50	$223.50
Purchase #3	$28.47	6.479%	$30.3146	$30.31	$30.30	$30.30
Purchase #4	$220.47	3.434%	$228.0409	$228.04	$228.05	$228.00
Purchase #5	$226.43	12.685%	$255.1526	$255.15	$255.15	$255.20
Purchase #6	$32.82	12.128%	$36.8004	$36.80	$36.80	$36.80
Purchase #7	$138.53	8.657%	$150.5225	$150.52	$150.50	$150.50
7 purchase totals =	$963.46		$1,056.2220	$1,056.21	$1,056.15	$1,056.20