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	$172.90	4.364%	$180.4454	$180.45	$180.45	$180.40
Purchase #2	$108.28	4.262%	$112.8949	$112.89	$112.90	$112.90
Purchase #3	$100.81	10.143%	$111.0352	$111.04	$111.05	$111.00
Purchase #4	$148.40	10.526%	$164.0206	$164.02	$164.00	$164.00
Purchase #5	$145.59	12.285%	$163.4757	$163.48	$163.50	$163.50
Purchase #6	$120.78	4.355%	$126.04	$126.04	$126.05	$126.00
Purchase #7	$63.53	8.426%	$68.883	$68.88	$68.90	$68.90
7 purchase totals =	$860.29		$926.7948	$926.80	$926.85	$926.70