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	$106.81	10.311%	$117.8232	$117.82	$117.80	$117.80
Purchase #2	$67.75	13.154%	$76.6618	$76.66	$76.65	$76.70
Purchase #3	$34.30	8.173%	$37.1033	$37.10	$37.10	$37.10
Purchase #4	$217.26	7.461%	$233.4698	$233.47	$233.45	$233.50
Purchase #5	$41.29	9.796%	$45.3348	$45.33	$45.35	$45.30
Purchase #6	$116.38	12.576%	$131.0159	$131.02	$131.00	$131.00
Purchase #7	$216.81	10.752%	$240.1214	$240.12	$240.10	$240.10
7 purchase totals =	$800.60		$881.5302	$881.52	$881.45	$881.50