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	$42.95	11.417%	$47.8536	$47.85	$47.85	$47.90
Purchase #2	$197.86	5.603%	$208.9461	$208.95	$208.95	$208.90
Purchase #3	$61.95	12.364%	$69.6095	$69.61	$69.60	$69.60
Purchase #4	$54.79	8.636%	$59.5217	$59.52	$59.50	$59.50
Purchase #5	$37.88	5.548%	$39.9816	$39.98	$40.00	$40.00
Purchase #6	$95.71	7.873%	$103.2452	$103.25	$103.25	$103.20
Purchase #7	$83.35	11.388%	$92.8419	$92.84	$92.85	$92.80
7 purchase totals =	$574.49		$621.9996	$622.00	$622.00	$621.90