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	$152.63	13.610%	$173.4029	$173.40	$173.40	$173.40
Purchase #2	$57.52	5.464%	$60.6629	$60.66	$60.65	$60.70
Purchase #3	$220.85	10.571%	$244.1961	$244.20	$244.20	$244.20
Purchase #4	$128.52	10.182%	$141.6059	$141.61	$141.60	$141.60
Purchase #5	$18.92	10.534%	$20.913	$20.91	$20.90	$20.90
Purchase #6	$75.45	6.178%	$80.1113	$80.11	$80.10	$80.10
Purchase #7	$63.48	3.282%	$65.5634	$65.56	$65.55	$65.60
7 purchase totals =	$717.37		$786.4555	$786.45	$786.40	$786.50