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	$232.95	11.539%	$259.8301	$259.83	$259.85	$259.80
Purchase #2	$36.82	9.569%	$40.3433	$40.34	$40.35	$40.30
Purchase #3	$227.34	6.838%	$242.8855	$242.89	$242.90	$242.90
Purchase #4	$76.43	12.442%	$85.9394	$85.94	$85.95	$85.90
Purchase #5	$140.99	13.547%	$160.0899	$160.09	$160.10	$160.10
Purchase #6	$95.38	5.576%	$100.6984	$100.70	$100.70	$100.70
Purchase #7	$143.51	12.535%	$161.499	$161.50	$161.50	$161.50
7 purchase totals =	$953.42		$1,051.2856	$1,051.29	$1,051.35	$1,051.20