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	$175.61	9.624%	$192.5107	$192.51	$192.50	$192.50
Purchase #2	$163.36	3.153%	$168.5107	$168.51	$168.50	$168.50
Purchase #3	$95.86	10.507%	$105.932	$105.93	$105.95	$105.90
Purchase #4	$107.41	8.327%	$116.354	$116.35	$116.35	$116.40
Purchase #5	$140.71	7.858%	$151.767	$151.77	$151.75	$151.80
Purchase #6	$216.76	3.499%	$224.3444	$224.34	$224.35	$224.30
Purchase #7	$132.56	5.406%	$139.7262	$139.73	$139.75	$139.70
7 purchase totals =	$1,032.27		$1,099.1450	$1,099.14	$1,099.15	$1,099.10