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	$95.51	5.805%	$101.0544	$101.05	$101.05	$101.10
Purchase #2	$83.47	8.684%	$90.7185	$90.72	$90.70	$90.70
Purchase #3	$121.35	7.497%	$130.4476	$130.45	$130.45	$130.40
Purchase #4	$5.40	7.339%	$5.7963	$5.80	$5.80	$5.80
Purchase #5	$92.46	3.682%	$95.8644	$95.86	$95.85	$95.90
Purchase #6	$120.74	5.872%	$127.8299	$127.83	$127.85	$127.80
Purchase #7	$102.61	10.688%	$113.577	$113.58	$113.60	$113.60
7 purchase totals =	$621.54		$665.2881	$665.29	$665.30	$665.30