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	$250.93	4.221%	$261.5218	$261.52	$261.50	$261.50
Purchase #2	$43.91	4.370%	$45.8289	$45.83	$45.85	$45.80
Purchase #3	$199.38	11.652%	$222.6118	$222.61	$222.60	$222.60
Purchase #4	$53.43	8.385%	$57.9101	$57.91	$57.90	$57.90
Purchase #5	$66.77	13.243%	$75.6124	$75.61	$75.60	$75.60
Purchase #6	$117.38	5.430%	$123.7537	$123.75	$123.75	$123.80
Purchase #7	$159.63	6.436%	$169.9038	$169.90	$169.90	$169.90
7 purchase totals =	$891.43		$957.1425	$957.13	$957.10	$957.10