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	$141.59	13.344%	$160.4838	$160.48	$160.50	$160.50
Purchase #2	$177.71	10.210%	$195.8542	$195.85	$195.85	$195.90
Purchase #3	$92.42	12.472%	$103.9466	$103.95	$103.95	$103.90
Purchase #4	$148.39	7.690%	$159.8012	$159.80	$159.80	$159.80
Purchase #5	$35.47	12.535%	$39.9162	$39.92	$39.90	$39.90
Purchase #6	$84.69	13.121%	$95.8022	$95.80	$95.80	$95.80
Purchase #7	$239.73	9.569%	$262.6698	$262.67	$262.65	$262.70
7 purchase totals =	$920.00		$1,018.4740	$1,018.47	$1,018.45	$1,018.50