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	$32.95	12.367%	$37.0249	$37.02	$37.00	$37.00
Purchase #2	$63.72	13.548%	$72.3528	$72.35	$72.35	$72.40
Purchase #3	$145.85	8.188%	$157.7922	$157.79	$157.80	$157.80
Purchase #4	$91.29	4.505%	$95.4026	$95.40	$95.40	$95.40
Purchase #5	$186.29	9.397%	$203.7957	$203.80	$203.80	$203.80
Purchase #6	$62.30	6.624%	$66.4268	$66.43	$66.45	$66.40
Purchase #7	$233.89	4.509%	$244.4361	$244.44	$244.45	$244.40
7 purchase totals =	$816.29		$877.2311	$877.23	$877.25	$877.20