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	$238.29	7.635%	$256.4834	$256.48	$256.50	$256.50
Purchase #2	$52.45	13.390%	$59.4731	$59.47	$59.45	$59.50
Purchase #3	$36.47	12.624%	$41.074	$41.07	$41.05	$41.10
Purchase #4	$194.35	11.482%	$216.6653	$216.67	$216.65	$216.70
Purchase #5	$116.67	4.216%	$121.5888	$121.59	$121.60	$121.60
Purchase #6	$51.60	8.313%	$55.8895	$55.89	$55.90	$55.90
Purchase #7	$234.85	4.566%	$245.5733	$245.57	$245.55	$245.60
7 purchase totals =	$924.68		$996.7474	$996.74	$996.70	$996.90