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	$119.40	9.644%	$130.9149	$130.91	$130.90	$130.90
Purchase #2	$77.79	10.153%	$85.688	$85.69	$85.70	$85.70
Purchase #3	$42.50	5.268%	$44.7389	$44.74	$44.75	$44.70
Purchase #4	$34.68	9.749%	$38.061	$38.06	$38.05	$38.10
Purchase #5	$45.43	11.517%	$50.6622	$50.66	$50.65	$50.70
Purchase #6	$26.27	13.861%	$29.9113	$29.91	$29.90	$29.90
Purchase #7	$157.47	7.248%	$168.8834	$168.88	$168.90	$168.90
7 purchase totals =	$503.54		$548.8597	$548.85	$548.85	$548.90