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	$90.40	7.487%	$97.1682	$97.17	$97.15	$97.20
Purchase #2	$162.70	4.862%	$170.6105	$170.61	$170.60	$170.60
Purchase #3	$29.80	7.843%	$32.1372	$32.14	$32.15	$32.10
Purchase #4	$231.77	10.759%	$256.7061	$256.71	$256.70	$256.70
Purchase #5	$140.63	4.115%	$146.4169	$146.42	$146.40	$146.40
Purchase #6	$200.50	4.148%	$208.8167	$208.82	$208.80	$208.80
Purchase #7	$192.29	4.240%	$200.4431	$200.44	$200.45	$200.40
7 purchase totals =	$1,048.09		$1,112.2987	$1,112.31	$1,112.25	$1,112.20