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	$62.94	6.691%	$67.1513	$67.15	$67.15	$67.20
Purchase #2	$17.90	5.186%	$18.8283	$18.83	$18.85	$18.80
Purchase #3	$138.73	7.106%	$148.5882	$148.59	$148.60	$148.60
Purchase #4	$47.75	6.594%	$50.8986	$50.90	$50.90	$50.90
Purchase #5	$219.48	12.763%	$247.4922	$247.49	$247.50	$247.50
Purchase #6	$166.79	3.650%	$172.8778	$172.88	$172.90	$172.90
Purchase #7	$225.65	13.279%	$255.6141	$255.61	$255.60	$255.60
7 purchase totals =	$879.24		$961.4505	$961.45	$961.50	$961.50