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	$99.27	7.162%	$106.3797	$106.38	$106.40	$106.40
Purchase #2	$167.50	8.566%	$181.8481	$181.85	$181.85	$181.80
Purchase #3	$123.78	11.764%	$138.3415	$138.34	$138.35	$138.30
Purchase #4	$199.58	4.460%	$208.4813	$208.48	$208.50	$208.50
Purchase #5	$173.45	11.177%	$192.8365	$192.84	$192.85	$192.80
Purchase #6	$57.43	5.382%	$60.5209	$60.52	$60.50	$60.50
Purchase #7	$113.97	8.338%	$123.4728	$123.47	$123.45	$123.50
7 purchase totals =	$934.98		$1,011.8808	$1,011.88	$1,011.90	$1,011.80