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	$45.95	7.563%	$49.4252	$49.43	$49.45	$49.40
Purchase #2	$91.75	12.108%	$102.8591	$102.86	$102.85	$102.90
Purchase #3	$218.89	7.152%	$234.545	$234.55	$234.55	$234.50
Purchase #4	$143.85	8.141%	$155.5608	$155.56	$155.55	$155.60
Purchase #5	$87.91	3.421%	$90.9174	$90.92	$90.90	$90.90
Purchase #6	$68.31	11.760%	$76.3433	$76.34	$76.35	$76.30
Purchase #7	$168.37	4.194%	$175.4314	$175.43	$175.45	$175.40
7 purchase totals =	$825.03		$885.0822	$885.09	$885.10	$885.00