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	$125.85	7.117%	$134.8067	$134.81	$134.80	$134.80
Purchase #2	$222.50	9.137%	$242.8298	$242.83	$242.85	$242.80
Purchase #3	$19.41	10.771%	$21.5007	$21.50	$21.50	$21.50
Purchase #4	$180.67	10.571%	$199.7686	$199.77	$199.75	$199.80
Purchase #5	$75.36	9.602%	$82.5961	$82.60	$82.60	$82.60
Purchase #6	$37.58	4.309%	$39.1993	$39.20	$39.20	$39.20
Purchase #7	$40.83	4.206%	$42.5473	$42.55	$42.55	$42.50
7 purchase totals =	$702.20		$763.2485	$763.26	$763.25	$763.20