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	$151.81	5.689%	$160.4465	$160.45	$160.45	$160.40
Purchase #2	$75.86	3.753%	$78.707	$78.71	$78.70	$78.70
Purchase #3	$157.71	9.524%	$172.7303	$172.73	$172.75	$172.70
Purchase #4	$51.57	9.724%	$56.5847	$56.58	$56.60	$56.60
Purchase #5	$201.41	4.787%	$211.0515	$211.05	$211.05	$211.10
Purchase #6	$72.35	8.139%	$78.2386	$78.24	$78.25	$78.20
Purchase #7	$129.76	10.760%	$143.7222	$143.72	$143.70	$143.70
7 purchase totals =	$840.47		$901.4808	$901.48	$901.50	$901.40