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	$97.49	7.586%	$104.8856	$104.89	$104.90	$104.90
Purchase #2	$140.79	3.415%	$145.598	$145.60	$145.60	$145.60
Purchase #3	$63.34	6.576%	$67.5052	$67.51	$67.50	$67.50
Purchase #4	$159.36	9.599%	$174.657	$174.66	$174.65	$174.70
Purchase #5	$133.36	13.575%	$151.4636	$151.46	$151.45	$151.50
Purchase #6	$123.83	11.381%	$137.9231	$137.92	$137.90	$137.90
Purchase #7	$111.61	10.750%	$123.6081	$123.61	$123.60	$123.60
7 purchase totals =	$829.78		$905.6406	$905.65	$905.60	$905.70