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	$39.47	9.631%	$43.2714	$43.27	$43.25	$43.30
Purchase #2	$244.56	4.388%	$255.2913	$255.29	$255.30	$255.30
Purchase #3	$44.59	11.624%	$49.7731	$49.77	$49.75	$49.80
Purchase #4	$231.74	10.675%	$256.4782	$256.48	$256.50	$256.50
Purchase #5	$81.26	7.238%	$87.1416	$87.14	$87.15	$87.10
Purchase #6	$92.29	3.502%	$95.522	$95.52	$95.50	$95.50
Purchase #7	$150.32	6.767%	$160.4922	$160.49	$160.50	$160.50
7 purchase totals =	$884.23		$947.9698	$947.96	$947.95	$948.00