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	$98.60	12.688%	$111.1104	$111.11	$111.10	$111.10
Purchase #2	$160.35	10.784%	$177.6421	$177.64	$177.65	$177.60
Purchase #3	$139.61	5.485%	$147.2676	$147.27	$147.25	$147.30
Purchase #4	$45.42	13.310%	$51.4654	$51.47	$51.45	$51.50
Purchase #5	$222.29	4.281%	$231.8062	$231.81	$231.80	$231.80
Purchase #6	$200.85	13.377%	$227.7177	$227.72	$227.70	$227.70
Purchase #7	$90.47	12.353%	$101.6458	$101.65	$101.65	$101.60
7 purchase totals =	$957.59		$1,048.6552	$1,048.67	$1,048.60	$1,048.60