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	$180.80	5.387%	$190.5397	$190.54	$190.55	$190.50
Purchase #2	$236.26	6.495%	$251.6051	$251.61	$251.60	$251.60
Purchase #3	$164.87	3.384%	$170.4492	$170.45	$170.45	$170.40
Purchase #4	$119.30	10.314%	$131.6046	$131.60	$131.60	$131.60
Purchase #5	$33.83	13.632%	$38.4417	$38.44	$38.45	$38.40
Purchase #6	$139.28	12.870%	$157.2053	$157.21	$157.20	$157.20
Purchase #7	$58.32	9.156%	$63.6598	$63.66	$63.65	$63.70
7 purchase totals =	$932.66		$1,003.5054	$1,003.51	$1,003.50	$1,003.40