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	$124.61	9.315%	$136.2174	$136.22	$136.20	$136.20
Purchase #2	$19.58	10.569%	$21.6494	$21.65	$21.65	$21.60
Purchase #3	$23.34	4.138%	$24.3058	$24.31	$24.30	$24.30
Purchase #4	$214.52	11.220%	$238.5891	$238.59	$238.60	$238.60
Purchase #5	$128.45	12.477%	$144.4767	$144.48	$144.50	$144.50
Purchase #6	$76.97	12.595%	$86.6644	$86.66	$86.65	$86.70
Purchase #7	$116.86	12.414%	$131.367	$131.37	$131.35	$131.40
7 purchase totals =	$704.33		$783.2698	$783.28	$783.25	$783.30