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	$192.68	13.604%	$218.8922	$218.89	$218.90	$218.90
Purchase #2	$136.48	3.504%	$141.2623	$141.26	$141.25	$141.30
Purchase #3	$37.88	12.698%	$42.69	$42.69	$42.70	$42.70
Purchase #4	$107.95	13.394%	$122.4088	$122.41	$122.40	$122.40
Purchase #5	$97.51	7.277%	$104.6058	$104.61	$104.60	$104.60
Purchase #6	$239.56	8.754%	$260.5311	$260.53	$260.55	$260.50
Purchase #7	$98.62	13.384%	$111.8193	$111.82	$111.80	$111.80
7 purchase totals =	$910.68		$1,002.2095	$1,002.21	$1,002.20	$1,002.20