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	$201.33	4.113%	$209.6107	$209.61	$209.60	$209.60
Purchase #2	$138.83	10.716%	$153.707	$153.71	$153.70	$153.70
Purchase #3	$216.45	5.113%	$227.5171	$227.52	$227.50	$227.50
Purchase #4	$87.98	13.672%	$100.0086	$100.01	$100.00	$100.00
Purchase #5	$208.37	3.794%	$216.2756	$216.28	$216.30	$216.30
Purchase #6	$166.49	13.611%	$189.151	$189.15	$189.15	$189.20
Purchase #7	$189.81	3.377%	$196.2199	$196.22	$196.20	$196.20
7 purchase totals =	$1,209.26		$1,292.4899	$1,292.50	$1,292.45	$1,292.50