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	$224.37	7.646%	$241.5253	$241.53	$241.55	$241.50
Purchase #2	$122.56	12.506%	$137.8874	$137.89	$137.90	$137.90
Purchase #3	$208.59	3.833%	$216.5853	$216.59	$216.60	$216.60
Purchase #4	$119.76	9.296%	$130.8929	$130.89	$130.90	$130.90
Purchase #5	$215.69	10.391%	$238.1023	$238.10	$238.10	$238.10
Purchase #6	$227.81	11.423%	$253.8327	$253.83	$253.85	$253.80
Purchase #7	$55.54	13.521%	$63.0496	$63.05	$63.05	$63.00
7 purchase totals =	$1,174.32		$1,281.8755	$1,281.88	$1,281.95	$1,281.80