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	$59.38	11.479%	$66.1962	$66.20	$66.20	$66.20
Purchase #2	$161.53	5.352%	$170.1751	$170.18	$170.20	$170.20
Purchase #3	$240.52	6.411%	$255.9397	$255.94	$255.95	$255.90
Purchase #4	$40.52	6.583%	$43.1874	$43.19	$43.20	$43.20
Purchase #5	$169.51	7.711%	$182.5809	$182.58	$182.60	$182.60
Purchase #6	$75.58	9.657%	$82.8788	$82.88	$82.90	$82.90
Purchase #7	$90.25	8.798%	$98.1902	$98.19	$98.20	$98.20
7 purchase totals =	$837.29		$899.1483	$899.16	$899.25	$899.20