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	$139.60	5.741%	$147.6144	$147.61	$147.60	$147.60
Purchase #2	$46.57	11.422%	$51.8892	$51.89	$51.90	$51.90
Purchase #3	$123.88	9.439%	$135.573	$135.57	$135.55	$135.60
Purchase #4	$152.39	13.381%	$172.7813	$172.78	$172.80	$172.80
Purchase #5	$34.91	4.677%	$36.5427	$36.54	$36.55	$36.50
Purchase #6	$125.96	4.282%	$131.3536	$131.35	$131.35	$131.40
Purchase #7	$199.58	3.604%	$206.7729	$206.77	$206.75	$206.80
7 purchase totals =	$822.89		$882.5271	$882.51	$882.50	$882.60