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	$116.72	13.871%	$132.9102	$132.91	$132.90	$132.90
Purchase #2	$213.62	11.642%	$238.4896	$238.49	$238.50	$238.50
Purchase #3	$126.80	4.298%	$132.2499	$132.25	$132.25	$132.20
Purchase #4	$231.65	6.695%	$247.159	$247.16	$247.15	$247.20
Purchase #5	$20.46	3.164%	$21.1074	$21.11	$21.10	$21.10
Purchase #6	$250.26	11.728%	$279.6105	$279.61	$279.60	$279.60
Purchase #7	$208.69	4.676%	$218.4483	$218.45	$218.45	$218.40
7 purchase totals =	$1,168.20		$1,269.9749	$1,269.98	$1,269.95	$1,269.90