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	$89.87	13.102%	$101.6448	$101.64	$101.65	$101.60
Purchase #2	$249.39	9.248%	$272.4536	$272.45	$272.45	$272.50
Purchase #3	$72.71	7.703%	$78.3109	$78.31	$78.30	$78.30
Purchase #4	$107.54	13.458%	$122.0127	$122.01	$122.00	$122.00
Purchase #5	$37.98	10.766%	$42.0689	$42.07	$42.05	$42.10
Purchase #6	$206.50	13.523%	$234.425	$234.43	$234.45	$234.40
Purchase #7	$173.89	4.114%	$181.0438	$181.04	$181.05	$181.00
7 purchase totals =	$937.88		$1,031.9597	$1,031.95	$1,031.95	$1,031.90