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	$196.66	13.203%	$222.625	$222.63	$222.65	$222.60
Purchase #2	$131.32	5.164%	$138.1014	$138.10	$138.10	$138.10
Purchase #3	$20.84	4.533%	$21.7847	$21.78	$21.80	$21.80
Purchase #4	$54.48	3.493%	$56.383	$56.38	$56.40	$56.40
Purchase #5	$101.36	10.534%	$112.0373	$112.04	$112.05	$112.00
Purchase #6	$168.56	11.797%	$188.445	$188.45	$188.45	$188.40
Purchase #7	$81.71	10.363%	$90.1776	$90.18	$90.20	$90.20
7 purchase totals =	$754.93		$829.5540	$829.56	$829.65	$829.50