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	$40.71	7.133%	$43.6138	$43.61	$43.60	$43.60
Purchase #2	$15.44	12.125%	$17.3121	$17.31	$17.30	$17.30
Purchase #3	$61.82	4.436%	$64.5623	$64.56	$64.55	$64.60
Purchase #4	$6.77	12.105%	$7.5895	$7.59	$7.60	$7.60
Purchase #5	$102.64	3.827%	$106.568	$106.57	$106.55	$106.60
Purchase #6	$65.31	10.501%	$72.1682	$72.17	$72.15	$72.20
Purchase #7	$73.60	4.186%	$76.6809	$76.68	$76.70	$76.70
7 purchase totals =	$366.29		$388.4948	$388.49	$388.45	$388.60