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	$185.82	7.533%	$199.8178	$199.82	$199.80	$199.80
Purchase #2	$129.66	11.709%	$144.8419	$144.84	$144.85	$144.80
Purchase #3	$63.27	12.526%	$71.1952	$71.20	$71.20	$71.20
Purchase #4	$164.89	8.839%	$179.4646	$179.46	$179.45	$179.50
Purchase #5	$216.79	3.605%	$224.6053	$224.61	$224.60	$224.60
Purchase #6	$72.83	5.653%	$76.9471	$76.95	$76.95	$76.90
Purchase #7	$172.89	4.455%	$180.5922	$180.59	$180.60	$180.60
7 purchase totals =	$1,006.15		$1,077.4641	$1,077.47	$1,077.45	$1,077.40