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	$113.32	3.809%	$117.6364	$117.64	$117.65	$117.60
Purchase #2	$193.54	7.705%	$208.4523	$208.45	$208.45	$208.50
Purchase #3	$20.56	4.517%	$21.4887	$21.49	$21.50	$21.50
Purchase #4	$139.68	9.714%	$153.2485	$153.25	$153.25	$153.20
Purchase #5	$24.96	8.390%	$27.0541	$27.05	$27.05	$27.10
Purchase #6	$216.35	11.152%	$240.4774	$240.48	$240.50	$240.50
Purchase #7	$99.52	3.345%	$102.8489	$102.85	$102.85	$102.80
7 purchase totals =	$807.93		$871.2063	$871.21	$871.25	$871.20