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	$78.49	5.706%	$82.9686	$82.97	$82.95	$83.00
Purchase #2	$66.56	13.678%	$75.6641	$75.66	$75.65	$75.70
Purchase #3	$237.85	7.333%	$255.2915	$255.29	$255.30	$255.30
Purchase #4	$212.62	7.334%	$228.2136	$228.21	$228.20	$228.20
Purchase #5	$55.80	7.329%	$59.8896	$59.89	$59.90	$59.90
Purchase #6	$34.27	7.853%	$36.9612	$36.96	$36.95	$37.00
Purchase #7	$19.65	3.141%	$20.2672	$20.27	$20.25	$20.30
7 purchase totals =	$705.24		$759.2558	$759.25	$759.20	$759.40