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	$95.30	8.681%	$103.573	$103.57	$103.55	$103.60
Purchase #2	$219.37	9.657%	$240.5546	$240.55	$240.55	$240.60
Purchase #3	$144.97	13.479%	$164.5105	$164.51	$164.50	$164.50
Purchase #4	$22.40	7.172%	$24.0065	$24.01	$24.00	$24.00
Purchase #5	$130.71	11.324%	$145.5116	$145.51	$145.50	$145.50
Purchase #6	$19.97	10.838%	$22.1343	$22.13	$22.15	$22.10
Purchase #7	$141.81	12.832%	$160.0071	$160.01	$160.00	$160.00
7 purchase totals =	$774.53		$860.2976	$860.29	$860.25	$860.30