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	$116.95	7.571%	$125.8043	$125.80	$125.80	$125.80
Purchase #2	$54.41	9.426%	$59.5387	$59.54	$59.55	$59.50
Purchase #3	$108.46	13.862%	$123.4947	$123.49	$123.50	$123.50
Purchase #4	$158.87	8.574%	$172.4915	$172.49	$172.50	$172.50
Purchase #5	$84.71	8.702%	$92.0815	$92.08	$92.10	$92.10
Purchase #6	$137.46	11.269%	$152.9504	$152.95	$152.95	$153.00
Purchase #7	$174.57	9.148%	$190.5397	$190.54	$190.55	$190.50
7 purchase totals =	$835.43		$916.9008	$916.89	$916.95	$916.90