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	$126.30	8.435%	$136.9534	$136.95	$136.95	$137.00
Purchase #2	$246.27	6.449%	$262.152	$262.15	$262.15	$262.20
Purchase #3	$144.52	11.848%	$161.6427	$161.64	$161.65	$161.60
Purchase #4	$93.37	7.327%	$100.2112	$100.21	$100.20	$100.20
Purchase #5	$93.34	6.573%	$99.4752	$99.48	$99.50	$99.50
Purchase #6	$68.79	13.785%	$78.2727	$78.27	$78.25	$78.30
Purchase #7	$215.93	9.680%	$236.832	$236.83	$236.85	$236.80
7 purchase totals =	$988.52		$1,075.5392	$1,075.53	$1,075.55	$1,075.60