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	$19.43	3.598%	$20.1291	$20.13	$20.15	$20.10
Purchase #2	$187.35	8.665%	$203.5839	$203.58	$203.60	$203.60
Purchase #3	$129.46	11.437%	$144.2663	$144.27	$144.25	$144.30
Purchase #4	$132.88	10.478%	$146.8032	$146.80	$146.80	$146.80
Purchase #5	$246.54	4.202%	$256.8996	$256.90	$256.90	$256.90
Purchase #6	$164.80	4.645%	$172.455	$172.46	$172.45	$172.50
Purchase #7	$99.77	10.385%	$110.1311	$110.13	$110.15	$110.10
7 purchase totals =	$980.23		$1,054.2682	$1,054.27	$1,054.30	$1,054.30