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	$241.63	3.312%	$249.6328	$249.63	$249.65	$249.60
Purchase #2	$137.53	10.526%	$152.0064	$152.01	$152.00	$152.00
Purchase #3	$237.49	8.870%	$258.5554	$258.56	$258.55	$258.60
Purchase #4	$43.77	3.151%	$45.1492	$45.15	$45.15	$45.10
Purchase #5	$212.95	4.594%	$222.7329	$222.73	$222.75	$222.70
Purchase #6	$242.54	11.297%	$269.9397	$269.94	$269.95	$269.90
Purchase #7	$216.81	10.175%	$238.8704	$238.87	$238.85	$238.90
7 purchase totals =	$1,332.72		$1,436.8868	$1,436.89	$1,436.90	$1,436.80