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	$208.37	3.541%	$215.7484	$215.75	$215.75	$215.70
Purchase #2	$65.78	10.351%	$72.5889	$72.59	$72.60	$72.60
Purchase #3	$137.30	8.316%	$148.7179	$148.72	$148.70	$148.70
Purchase #4	$167.84	13.487%	$190.4766	$190.48	$190.50	$190.50
Purchase #5	$41.35	12.680%	$46.5932	$46.59	$46.60	$46.60
Purchase #6	$204.73	10.132%	$225.4732	$225.47	$225.45	$225.50
Purchase #7	$178.34	7.641%	$191.967	$191.97	$191.95	$192.00
7 purchase totals =	$1,003.71		$1,091.5652	$1,091.57	$1,091.55	$1,091.60