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	$192.80	13.171%	$218.1937	$218.19	$218.20	$218.20
Purchase #2	$198.85	11.708%	$222.1314	$222.13	$222.15	$222.10
Purchase #3	$153.26	12.748%	$172.7976	$172.80	$172.80	$172.80
Purchase #4	$142.54	10.482%	$157.481	$157.48	$157.50	$157.50
Purchase #5	$100.69	9.112%	$109.8649	$109.86	$109.85	$109.90
Purchase #6	$39.83	11.595%	$44.4483	$44.45	$44.45	$44.40
Purchase #7	$148.93	8.624%	$161.7737	$161.77	$161.75	$161.80
7 purchase totals =	$976.90		$1,086.6906	$1,086.68	$1,086.70	$1,086.70