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	$59.71	4.394%	$62.3337	$62.33	$62.35	$62.30
Purchase #2	$202.34	7.296%	$217.1027	$217.10	$217.10	$217.10
Purchase #3	$189.77	9.739%	$208.2517	$208.25	$208.25	$208.30
Purchase #4	$171.37	12.496%	$192.7844	$192.78	$192.80	$192.80
Purchase #5	$77.66	12.370%	$87.2665	$87.27	$87.25	$87.30
Purchase #6	$89.73	12.402%	$100.8583	$100.86	$100.85	$100.90
Purchase #7	$102.94	10.208%	$113.4481	$113.45	$113.45	$113.40
7 purchase totals =	$893.52		$982.0454	$982.04	$982.05	$982.10