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	$216.57	5.571%	$228.6351	$228.64	$228.65	$228.60
Purchase #2	$208.53	13.541%	$236.767	$236.77	$236.75	$236.80
Purchase #3	$205.47	9.290%	$224.5582	$224.56	$224.55	$224.60
Purchase #4	$38.75	9.297%	$42.3526	$42.35	$42.35	$42.40
Purchase #5	$114.78	11.412%	$127.8787	$127.88	$127.90	$127.90
Purchase #6	$153.66	12.358%	$172.6493	$172.65	$172.65	$172.60
Purchase #7	$202.85	9.762%	$222.6522	$222.65	$222.65	$222.70
7 purchase totals =	$1,140.61		$1,255.4931	$1,255.50	$1,255.50	$1,255.60