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	$194.42	13.500%	$220.6667	$220.67	$220.65	$220.70
Purchase #2	$129.57	7.787%	$139.6596	$139.66	$139.65	$139.70
Purchase #3	$165.80	7.559%	$178.3328	$178.33	$178.35	$178.30
Purchase #4	$223.33	13.739%	$254.0133	$254.01	$254.00	$254.00
Purchase #5	$128.54	12.697%	$144.8607	$144.86	$144.85	$144.90
Purchase #6	$95.82	5.171%	$100.7749	$100.77	$100.75	$100.80
Purchase #7	$193.85	10.822%	$214.8284	$214.83	$214.85	$214.80
7 purchase totals =	$1,131.33		$1,253.1364	$1,253.13	$1,253.10	$1,253.20