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	$18.83	4.352%	$19.6495	$19.65	$19.65	$19.60
Purchase #2	$182.31	13.188%	$206.353	$206.35	$206.35	$206.40
Purchase #3	$76.52	7.538%	$82.2881	$82.29	$82.30	$82.30
Purchase #4	$192.78	3.784%	$200.0748	$200.07	$200.05	$200.10
Purchase #5	$88.48	10.287%	$97.5819	$97.58	$97.60	$97.60
Purchase #6	$250.52	11.362%	$278.9841	$278.98	$279.00	$279.00
Purchase #7	$154.74	4.439%	$161.6089	$161.61	$161.60	$161.60
7 purchase totals =	$964.18		$1,046.5403	$1,046.53	$1,046.55	$1,046.60