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	$81.90	4.344%	$85.4577	$85.46	$85.45	$85.50
Purchase #2	$161.39	4.175%	$168.128	$168.13	$168.15	$168.10
Purchase #3	$160.59	6.362%	$170.8067	$170.81	$170.80	$170.80
Purchase #4	$238.56	10.827%	$264.3889	$264.39	$264.40	$264.40
Purchase #5	$69.90	11.269%	$77.777	$77.78	$77.80	$77.80
Purchase #6	$47.91	13.831%	$54.5364	$54.54	$54.55	$54.50
Purchase #7	$124.37	10.648%	$137.6129	$137.61	$137.60	$137.60
7 purchase totals =	$884.62		$958.7076	$958.72	$958.75	$958.70