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	$101.71	3.680%	$105.4529	$105.45	$105.45	$105.50
Purchase #2	$85.37	6.438%	$90.8661	$90.87	$90.85	$90.90
Purchase #3	$102.38	5.342%	$107.8491	$107.85	$107.85	$107.80
Purchase #4	$231.57	7.685%	$249.3662	$249.37	$249.35	$249.40
Purchase #5	$63.35	12.403%	$71.2073	$71.21	$71.20	$71.20
Purchase #6	$158.38	4.626%	$165.7067	$165.71	$165.70	$165.70
Purchase #7	$134.73	8.792%	$146.5755	$146.58	$146.60	$146.60
7 purchase totals =	$877.49		$937.0238	$937.04	$937.00	$937.10