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	$113.83	8.506%	$123.5124	$123.51	$123.50	$123.50
Purchase #2	$177.52	6.266%	$188.6434	$188.64	$188.65	$188.60
Purchase #3	$137.66	10.858%	$152.6071	$152.61	$152.60	$152.60
Purchase #4	$150.99	4.334%	$157.5339	$157.53	$157.55	$157.50
Purchase #5	$50.70	5.805%	$53.6431	$53.64	$53.65	$53.60
Purchase #6	$76.25	13.430%	$86.4904	$86.49	$86.50	$86.50
Purchase #7	$182.67	4.656%	$191.1751	$191.18	$191.20	$191.20
7 purchase totals =	$889.62		$953.6054	$953.60	$953.65	$953.50