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	$108.70	12.194%	$121.9549	$121.95	$121.95	$122.00
Purchase #2	$76.58	8.246%	$82.8948	$82.89	$82.90	$82.90
Purchase #3	$117.35	11.275%	$130.5812	$130.58	$130.60	$130.60
Purchase #4	$197.48	3.536%	$204.4629	$204.46	$204.45	$204.50
Purchase #5	$244.72	12.438%	$275.1583	$275.16	$275.15	$275.20
Purchase #6	$167.31	11.823%	$187.0911	$187.09	$187.10	$187.10
Purchase #7	$227.34	11.515%	$253.5182	$253.52	$253.50	$253.50
7 purchase totals =	$1,139.48		$1,255.6614	$1,255.65	$1,255.65	$1,255.80