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	$141.61	6.323%	$150.564	$150.56	$150.55	$150.60
Purchase #2	$177.47	12.358%	$199.4017	$199.40	$199.40	$199.40
Purchase #3	$21.76	5.790%	$23.0199	$23.02	$23.00	$23.00
Purchase #4	$220.29	3.325%	$227.6146	$227.61	$227.60	$227.60
Purchase #5	$224.45	7.764%	$241.8763	$241.88	$241.90	$241.90
Purchase #6	$108.31	7.644%	$116.5892	$116.59	$116.60	$116.60
Purchase #7	$118.27	11.852%	$132.2874	$132.29	$132.30	$132.30
7 purchase totals =	$1,012.16		$1,091.3531	$1,091.35	$1,091.35	$1,091.40