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	$212.60	6.515%	$226.4509	$226.45	$226.45	$226.50
Purchase #2	$149.50	5.539%	$157.7808	$157.78	$157.80	$157.80
Purchase #3	$79.60	13.252%	$90.1486	$90.15	$90.15	$90.10
Purchase #4	$224.46	4.427%	$234.3968	$234.40	$234.40	$234.40
Purchase #5	$216.34	12.397%	$243.1597	$243.16	$243.15	$243.20
Purchase #6	$11.47	12.313%	$12.8823	$12.88	$12.90	$12.90
Purchase #7	$50.66	8.649%	$55.0416	$55.04	$55.05	$55.00
7 purchase totals =	$944.63		$1,019.8607	$1,019.86	$1,019.90	$1,019.90