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	$118.43	11.335%	$131.854	$131.85	$131.85	$131.90
Purchase #2	$16.34	11.316%	$18.189	$18.19	$18.20	$18.20
Purchase #3	$141.84	13.570%	$161.0877	$161.09	$161.10	$161.10
Purchase #4	$86.93	5.685%	$91.872	$91.87	$91.85	$91.90
Purchase #5	$242.89	13.418%	$275.481	$275.48	$275.50	$275.50
Purchase #6	$41.96	3.519%	$43.4366	$43.44	$43.45	$43.40
Purchase #7	$132.45	8.110%	$143.1917	$143.19	$143.20	$143.20
7 purchase totals =	$780.84		$865.1120	$865.11	$865.15	$865.20