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	$146.88	3.797%	$152.457	$152.46	$152.45	$152.50
Purchase #2	$78.90	13.402%	$89.4742	$89.47	$89.45	$89.50
Purchase #3	$231.47	13.258%	$262.1583	$262.16	$262.15	$262.20
Purchase #4	$250.46	10.807%	$277.5272	$277.53	$277.55	$277.50
Purchase #5	$129.45	7.551%	$139.2248	$139.22	$139.20	$139.20
Purchase #6	$101.60	6.717%	$108.4245	$108.42	$108.40	$108.40
Purchase #7	$201.72	6.496%	$214.8237	$214.82	$214.80	$214.80
7 purchase totals =	$1,140.48		$1,244.0897	$1,244.08	$1,244.00	$1,244.10