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	$132.82	5.294%	$139.8515	$139.85	$139.85	$139.90
Purchase #2	$8.87	11.687%	$9.9066	$9.91	$9.90	$9.90
Purchase #3	$100.63	10.727%	$111.4246	$111.42	$111.40	$111.40
Purchase #4	$37.48	4.625%	$39.2135	$39.21	$39.20	$39.20
Purchase #5	$81.43	13.548%	$92.4621	$92.46	$92.45	$92.50
Purchase #6	$59.88	6.630%	$63.85	$63.85	$63.85	$63.90
Purchase #7	$203.26	5.496%	$214.4312	$214.43	$214.45	$214.40
7 purchase totals =	$624.37		$671.1395	$671.13	$671.10	$671.20