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	$188.95	5.557%	$199.45	$199.45	$199.45	$199.50
Purchase #2	$208.55	6.155%	$221.3863	$221.39	$221.40	$221.40
Purchase #3	$189.59	6.796%	$202.4745	$202.47	$202.45	$202.50
Purchase #4	$100.61	8.675%	$109.3379	$109.34	$109.35	$109.30
Purchase #5	$57.71	5.176%	$60.6971	$60.70	$60.70	$60.70
Purchase #6	$78.85	4.648%	$82.5149	$82.51	$82.50	$82.50
Purchase #7	$23.96	6.837%	$25.5981	$25.60	$25.60	$25.60
7 purchase totals =	$848.22		$901.4588	$901.46	$901.45	$901.50