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	$59.52	12.402%	$66.9017	$66.90	$66.90	$66.90
Purchase #2	$113.43	3.493%	$117.3921	$117.39	$117.40	$117.40
Purchase #3	$28.72	7.306%	$30.8183	$30.82	$30.80	$30.80
Purchase #4	$91.62	5.336%	$96.5088	$96.51	$96.50	$96.50
Purchase #5	$51.85	9.597%	$56.826	$56.83	$56.85	$56.80
Purchase #6	$101.52	8.132%	$109.7756	$109.78	$109.80	$109.80
Purchase #7	$232.83	6.610%	$248.2201	$248.22	$248.20	$248.20
7 purchase totals =	$679.49		$726.4426	$726.45	$726.45	$726.40