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	$56.71	4.494%	$59.2585	$59.26	$59.25	$59.30
Purchase #2	$59.57	6.344%	$63.3491	$63.35	$63.35	$63.30
Purchase #3	$143.80	9.257%	$157.1116	$157.11	$157.10	$157.10
Purchase #4	$223.52	10.703%	$247.4433	$247.44	$247.45	$247.40
Purchase #5	$16.74	13.250%	$18.9581	$18.96	$18.95	$19.00
Purchase #6	$223.39	12.170%	$250.5766	$250.58	$250.60	$250.60
Purchase #7	$83.95	7.753%	$90.4586	$90.46	$90.45	$90.50
7 purchase totals =	$807.68		$887.1558	$887.16	$887.15	$887.20