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	$33.53	10.833%	$37.1623	$37.16	$37.15	$37.20
Purchase #2	$155.49	10.854%	$172.3669	$172.37	$172.35	$172.40
Purchase #3	$235.83	10.299%	$260.1181	$260.12	$260.10	$260.10
Purchase #4	$221.30	10.264%	$244.0142	$244.01	$244.00	$244.00
Purchase #5	$140.58	4.828%	$147.3672	$147.37	$147.35	$147.40
Purchase #6	$223.85	6.467%	$238.3264	$238.33	$238.35	$238.30
Purchase #7	$23.33	3.313%	$24.1029	$24.10	$24.10	$24.10
7 purchase totals =	$1,033.91		$1,123.4580	$1,123.46	$1,123.40	$1,123.50