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	$138.50	8.776%	$150.6548	$150.65	$150.65	$150.70
Purchase #2	$138.43	13.484%	$157.0959	$157.10	$157.10	$157.10
Purchase #3	$150.53	11.834%	$168.3437	$168.34	$168.35	$168.30
Purchase #4	$78.52	4.836%	$82.3172	$82.32	$82.30	$82.30
Purchase #5	$222.93	12.722%	$251.2912	$251.29	$251.30	$251.30
Purchase #6	$204.29	9.390%	$223.4728	$223.47	$223.45	$223.50
Purchase #7	$100.32	13.483%	$113.8461	$113.85	$113.85	$113.80
7 purchase totals =	$1,033.52		$1,147.0217	$1,147.02	$1,147.00	$1,147.00