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	$93.35	5.288%	$98.2863	$98.29	$98.30	$98.30
Purchase #2	$187.61	4.844%	$196.6978	$196.70	$196.70	$196.70
Purchase #3	$246.94	9.182%	$269.614	$269.61	$269.60	$269.60
Purchase #4	$198.35	5.160%	$208.5849	$208.58	$208.60	$208.60
Purchase #5	$43.27	7.263%	$46.4127	$46.41	$46.40	$46.40
Purchase #6	$187.37	5.680%	$198.0126	$198.01	$198.00	$198.00
Purchase #7	$24.49	5.619%	$25.8661	$25.87	$25.85	$25.90
7 purchase totals =	$981.38		$1,043.4744	$1,043.47	$1,043.45	$1,043.50