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	$195.91	12.730%	$220.8493	$220.85	$220.85	$220.80
Purchase #2	$61.69	9.536%	$67.5728	$67.57	$67.55	$67.60
Purchase #3	$138.86	8.266%	$150.3382	$150.34	$150.35	$150.30
Purchase #4	$11.43	8.209%	$12.3683	$12.37	$12.35	$12.40
Purchase #5	$179.50	9.244%	$196.093	$196.09	$196.10	$196.10
Purchase #6	$119.50	12.685%	$134.6586	$134.66	$134.65	$134.70
Purchase #7	$206.50	13.321%	$234.0079	$234.01	$234.00	$234.00
7 purchase totals =	$913.39		$1,015.8881	$1,015.89	$1,015.85	$1,015.90