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	$205.42	10.856%	$227.7204	$227.72	$227.70	$227.70
Purchase #2	$94.90	11.184%	$105.5136	$105.51	$105.50	$105.50
Purchase #3	$146.94	7.733%	$158.3029	$158.30	$158.30	$158.30
Purchase #4	$96.74	4.116%	$100.7218	$100.72	$100.70	$100.70
Purchase #5	$216.75	12.166%	$243.1198	$243.12	$243.10	$243.10
Purchase #6	$180.30	5.710%	$190.5951	$190.60	$190.60	$190.60
Purchase #7	$182.43	12.400%	$205.0513	$205.05	$205.05	$205.10
7 purchase totals =	$1,123.48		$1,231.0249	$1,231.02	$1,230.95	$1,231.00