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	$7.31	12.853%	$8.2496	$8.25	$8.25	$8.20
Purchase #2	$78.80	10.303%	$86.9188	$86.92	$86.90	$86.90
Purchase #3	$189.83	5.203%	$199.7069	$199.71	$199.70	$199.70
Purchase #4	$40.95	6.661%	$43.6777	$43.68	$43.70	$43.70
Purchase #5	$69.37	10.291%	$76.5089	$76.51	$76.50	$76.50
Purchase #6	$142.92	13.546%	$162.2799	$162.28	$162.30	$162.30
Purchase #7	$45.90	9.496%	$50.2587	$50.26	$50.25	$50.30
7 purchase totals =	$575.08		$627.6005	$627.61	$627.60	$627.60