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	$225.28	6.459%	$239.8308	$239.83	$239.85	$239.80
Purchase #2	$240.61	8.239%	$260.4339	$260.43	$260.45	$260.40
Purchase #3	$134.86	5.198%	$141.87	$141.87	$141.85	$141.90
Purchase #4	$213.52	4.577%	$223.2928	$223.29	$223.30	$223.30
Purchase #5	$243.67	13.211%	$275.8612	$275.86	$275.85	$275.90
Purchase #6	$88.27	4.738%	$92.4522	$92.45	$92.45	$92.50
Purchase #7	$162.40	11.347%	$180.8275	$180.83	$180.85	$180.80
7 purchase totals =	$1,308.61		$1,414.5684	$1,414.56	$1,414.60	$1,414.60