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	$137.85	9.209%	$150.5446	$150.54	$150.55	$150.50
Purchase #2	$53.68	3.676%	$55.6533	$55.65	$55.65	$55.70
Purchase #3	$36.77	7.485%	$39.5222	$39.52	$39.50	$39.50
Purchase #4	$233.77	4.518%	$244.3317	$244.33	$244.35	$244.30
Purchase #5	$226.29	9.395%	$247.5499	$247.55	$247.55	$247.50
Purchase #6	$158.30	9.150%	$172.7845	$172.78	$172.80	$172.80
Purchase #7	$175.72	8.593%	$190.8196	$190.82	$190.80	$190.80
7 purchase totals =	$1,022.38		$1,101.2058	$1,101.19	$1,101.20	$1,101.10