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	$76.46	11.802%	$85.4838	$85.48	$85.50	$85.50
Purchase #2	$108.51	3.501%	$112.3089	$112.31	$112.30	$112.30
Purchase #3	$13.90	4.798%	$14.5669	$14.57	$14.55	$14.60
Purchase #4	$241.61	6.136%	$256.4352	$256.44	$256.45	$256.40
Purchase #5	$222.69	5.320%	$234.5371	$234.54	$234.55	$234.50
Purchase #6	$130.66	6.733%	$139.4573	$139.46	$139.45	$139.50
Purchase #7	$27.77	6.482%	$29.5701	$29.57	$29.55	$29.60
7 purchase totals =	$821.60		$872.3593	$872.37	$872.35	$872.40