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	$164.95	11.832%	$184.4669	$184.47	$184.45	$184.50
Purchase #2	$240.93	13.771%	$274.1085	$274.11	$274.10	$274.10
Purchase #3	$213.47	5.578%	$225.3774	$225.38	$225.40	$225.40
Purchase #4	$126.33	11.555%	$140.9274	$140.93	$140.95	$140.90
Purchase #5	$35.66	12.460%	$40.1032	$40.10	$40.10	$40.10
Purchase #6	$85.37	6.213%	$90.674	$90.67	$90.65	$90.70
Purchase #7	$66.71	12.389%	$74.9747	$74.97	$74.95	$75.00
7 purchase totals =	$933.42		$1,030.6321	$1,030.63	$1,030.60	$1,030.70