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	$229.50	3.244%	$236.945	$236.95	$236.95	$236.90
Purchase #2	$219.78	3.871%	$228.2877	$228.29	$228.30	$228.30
Purchase #3	$192.81	12.173%	$216.2808	$216.28	$216.30	$216.30
Purchase #4	$65.29	11.167%	$72.5809	$72.58	$72.60	$72.60
Purchase #5	$124.27	10.624%	$137.4724	$137.47	$137.45	$137.50
Purchase #6	$201.64	10.614%	$223.0421	$223.04	$223.05	$223.00
Purchase #7	$106.27	13.402%	$120.5123	$120.51	$120.50	$120.50
7 purchase totals =	$1,139.56		$1,235.1212	$1,235.12	$1,235.15	$1,235.10