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	$48.62	11.754%	$54.3348	$54.33	$54.35	$54.30
Purchase #2	$66.40	8.682%	$72.1648	$72.16	$72.15	$72.20
Purchase #3	$212.69	5.105%	$223.5478	$223.55	$223.55	$223.50
Purchase #4	$152.99	7.590%	$164.6019	$164.60	$164.60	$164.60
Purchase #5	$78.57	11.803%	$87.8436	$87.84	$87.85	$87.80
Purchase #6	$101.27	11.235%	$112.6477	$112.65	$112.65	$112.60
Purchase #7	$35.25	13.671%	$40.069	$40.07	$40.05	$40.10
7 purchase totals =	$695.79		$755.2096	$755.20	$755.20	$755.10