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	$81.85	10.406%	$90.3673	$90.37	$90.35	$90.40
Purchase #2	$155.26	5.795%	$164.2573	$164.26	$164.25	$164.30
Purchase #3	$219.89	5.198%	$231.3199	$231.32	$231.30	$231.30
Purchase #4	$185.42	12.332%	$208.286	$208.29	$208.30	$208.30
Purchase #5	$22.39	8.576%	$24.3102	$24.31	$24.30	$24.30
Purchase #6	$177.37	7.377%	$190.4546	$190.45	$190.45	$190.50
Purchase #7	$189.50	9.174%	$206.8847	$206.88	$206.90	$206.90
7 purchase totals =	$1,031.68		$1,115.8800	$1,115.88	$1,115.85	$1,116.00