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	$36.59	4.147%	$38.1074	$38.11	$38.10	$38.10
Purchase #2	$33.72	12.562%	$37.9559	$37.96	$37.95	$38.00
Purchase #3	$120.78	9.794%	$132.6092	$132.61	$132.60	$132.60
Purchase #4	$209.62	4.756%	$219.5895	$219.59	$219.60	$219.60
Purchase #5	$139.62	11.311%	$155.4124	$155.41	$155.40	$155.40
Purchase #6	$151.88	13.861%	$172.9321	$172.93	$172.95	$172.90
Purchase #7	$192.85	8.433%	$209.113	$209.11	$209.10	$209.10
7 purchase totals =	$885.06		$965.7195	$965.72	$965.70	$965.70