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	$87.53	12.367%	$98.3548	$98.35	$98.35	$98.40
Purchase #2	$40.95	10.472%	$45.2383	$45.24	$45.25	$45.20
Purchase #3	$214.51	8.698%	$233.1681	$233.17	$233.15	$233.20
Purchase #4	$165.73	9.713%	$181.8274	$181.83	$181.85	$181.80
Purchase #5	$34.28	5.487%	$36.1609	$36.16	$36.15	$36.20
Purchase #6	$200.35	13.779%	$227.9562	$227.96	$227.95	$228.00
Purchase #7	$73.38	7.267%	$78.7125	$78.71	$78.70	$78.70
7 purchase totals =	$816.73		$901.4182	$901.42	$901.40	$901.50