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	$206.60	8.157%	$223.4524	$223.45	$223.45	$223.50
Purchase #2	$10.77	6.327%	$11.4514	$11.45	$11.45	$11.50
Purchase #3	$70.81	9.467%	$77.5136	$77.51	$77.50	$77.50
Purchase #4	$235.39	12.575%	$264.9903	$264.99	$265.00	$265.00
Purchase #5	$100.50	10.260%	$110.8113	$110.81	$110.80	$110.80
Purchase #6	$203.76	9.131%	$222.3653	$222.37	$222.35	$222.40
Purchase #7	$59.88	8.266%	$64.8297	$64.83	$64.85	$64.80
7 purchase totals =	$887.71		$975.4140	$975.41	$975.40	$975.50