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	$186.86	6.741%	$199.4562	$199.46	$199.45	$199.50
Purchase #2	$206.55	7.732%	$222.5204	$222.52	$222.50	$222.50
Purchase #3	$37.42	4.697%	$39.1776	$39.18	$39.20	$39.20
Purchase #4	$15.72	8.561%	$17.0658	$17.07	$17.05	$17.10
Purchase #5	$128.32	6.525%	$136.6929	$136.69	$136.70	$136.70
Purchase #6	$198.63	6.468%	$211.4774	$211.48	$211.50	$211.50
Purchase #7	$88.29	3.485%	$91.3669	$91.37	$91.35	$91.40
7 purchase totals =	$861.79		$917.7572	$917.77	$917.75	$917.90