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	$102.78	9.531%	$112.576	$112.58	$112.60	$112.60
Purchase #2	$94.36	10.733%	$104.4877	$104.49	$104.50	$104.50
Purchase #3	$146.82	5.771%	$155.293	$155.29	$155.30	$155.30
Purchase #4	$30.74	4.584%	$32.1491	$32.15	$32.15	$32.10
Purchase #5	$241.50	5.364%	$254.4541	$254.45	$254.45	$254.50
Purchase #6	$168.88	9.352%	$184.6737	$184.67	$184.65	$184.70
Purchase #7	$100.92	4.705%	$105.6683	$105.67	$105.65	$105.70
7 purchase totals =	$886.00		$949.3019	$949.30	$949.30	$949.40