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	$78.34	9.664%	$85.9108	$85.91	$85.90	$85.90
Purchase #2	$76.67	7.105%	$82.1174	$82.12	$82.10	$82.10
Purchase #3	$153.37	5.356%	$161.5845	$161.58	$161.60	$161.60
Purchase #4	$223.39	10.504%	$246.8549	$246.85	$246.85	$246.90
Purchase #5	$131.54	5.869%	$139.2601	$139.26	$139.25	$139.30
Purchase #6	$37.33	11.464%	$41.6095	$41.61	$41.60	$41.60
Purchase #7	$10.77	9.691%	$11.8137	$11.81	$11.80	$11.80
7 purchase totals =	$711.41		$769.1509	$769.14	$769.10	$769.20