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	$104.27	8.630%	$113.2685	$113.27	$113.25	$113.30
Purchase #2	$75.36	4.641%	$78.8575	$78.86	$78.85	$78.90
Purchase #3	$233.93	6.790%	$249.8138	$249.81	$249.80	$249.80
Purchase #4	$106.54	12.528%	$119.8873	$119.89	$119.90	$119.90
Purchase #5	$69.82	11.719%	$78.0022	$78.00	$78.00	$78.00
Purchase #6	$102.83	10.130%	$113.2467	$113.25	$113.25	$113.20
Purchase #7	$179.87	5.667%	$190.0632	$190.06	$190.05	$190.10
7 purchase totals =	$872.62		$943.1392	$943.14	$943.10	$943.20