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	$41.82	9.338%	$45.7252	$45.73	$45.75	$45.70
Purchase #2	$122.68	13.404%	$139.124	$139.12	$139.10	$139.10
Purchase #3	$122.63	10.502%	$135.5086	$135.51	$135.50	$135.50
Purchase #4	$192.82	8.313%	$208.8491	$208.85	$208.85	$208.80
Purchase #5	$72.45	3.870%	$75.2538	$75.25	$75.25	$75.30
Purchase #6	$98.90	12.762%	$111.5216	$111.52	$111.50	$111.50
Purchase #7	$14.37	10.591%	$15.8919	$15.89	$15.90	$15.90
7 purchase totals =	$665.67		$731.8742	$731.87	$731.85	$731.80