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	$189.85	5.381%	$200.0658	$200.07	$200.05	$200.10
Purchase #2	$124.90	10.216%	$137.6598	$137.66	$137.65	$137.70
Purchase #3	$213.25	8.746%	$231.9008	$231.90	$231.90	$231.90
Purchase #4	$111.90	10.460%	$123.6047	$123.60	$123.60	$123.60
Purchase #5	$58.91	4.592%	$61.6151	$61.62	$61.60	$61.60
Purchase #6	$59.71	11.512%	$66.5838	$66.58	$66.60	$66.60
Purchase #7	$175.83	11.606%	$196.2368	$196.24	$196.25	$196.20
7 purchase totals =	$934.35		$1,017.6668	$1,017.67	$1,017.65	$1,017.70