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	$66.56	8.724%	$72.3667	$72.37	$72.35	$72.40
Purchase #2	$93.56	6.785%	$99.908	$99.91	$99.90	$99.90
Purchase #3	$212.59	5.163%	$223.566	$223.57	$223.55	$223.60
Purchase #4	$203.39	5.651%	$214.8836	$214.88	$214.90	$214.90
Purchase #5	$18.58	3.245%	$19.1829	$19.18	$19.20	$19.20
Purchase #6	$40.39	13.484%	$45.8362	$45.84	$45.85	$45.80
Purchase #7	$170.28	11.294%	$189.5114	$189.51	$189.50	$189.50
7 purchase totals =	$805.35		$865.2548	$865.26	$865.25	$865.30