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	$34.43	9.103%	$37.5642	$37.56	$37.55	$37.60
Purchase #2	$7.70	10.350%	$8.497	$8.50	$8.50	$8.50
Purchase #3	$118.48	4.759%	$124.1185	$124.12	$124.10	$124.10
Purchase #4	$40.50	13.451%	$45.9477	$45.95	$45.95	$45.90
Purchase #5	$80.26	7.614%	$86.371	$86.37	$86.35	$86.40
Purchase #6	$71.38	10.257%	$78.7014	$78.70	$78.70	$78.70
Purchase #7	$81.44	11.502%	$90.8072	$90.81	$90.80	$90.80
7 purchase totals =	$434.19		$472.0070	$472.01	$471.95	$472.00