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	$67.77	13.482%	$76.9068	$76.91	$76.90	$76.90
Purchase #2	$70.42	3.379%	$72.7995	$72.80	$72.80	$72.80
Purchase #3	$219.59	8.837%	$238.9952	$239.00	$239.00	$239.00
Purchase #4	$69.81	12.406%	$78.4706	$78.47	$78.45	$78.50
Purchase #5	$218.47	3.561%	$226.2497	$226.25	$226.25	$226.20
Purchase #6	$208.34	6.249%	$221.3592	$221.36	$221.35	$221.40
Purchase #7	$169.57	7.388%	$182.0978	$182.10	$182.10	$182.10
7 purchase totals =	$1,023.97		$1,096.8788	$1,096.89	$1,096.85	$1,096.90