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	$220.80	7.525%	$237.4152	$237.42	$237.40	$237.40
Purchase #2	$15.93	12.327%	$17.8937	$17.89	$17.90	$17.90
Purchase #3	$85.48	4.719%	$89.5138	$89.51	$89.50	$89.50
Purchase #4	$80.46	12.493%	$90.5119	$90.51	$90.50	$90.50
Purchase #5	$148.36	8.253%	$160.6042	$160.60	$160.60	$160.60
Purchase #6	$109.43	3.145%	$112.8716	$112.87	$112.85	$112.90
Purchase #7	$111.53	4.200%	$116.2143	$116.21	$116.20	$116.20
7 purchase totals =	$771.99		$825.0247	$825.01	$824.95	$825.00