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	$145.75	3.733%	$151.1908	$151.19	$151.20	$151.20
Purchase #2	$103.78	5.392%	$109.3758	$109.38	$109.40	$109.40
Purchase #3	$42.94	11.692%	$47.9605	$47.96	$47.95	$48.00
Purchase #4	$81.81	5.779%	$86.5378	$86.54	$86.55	$86.50
Purchase #5	$205.58	10.527%	$227.2214	$227.22	$227.20	$227.20
Purchase #6	$130.38	5.705%	$137.8182	$137.82	$137.80	$137.80
Purchase #7	$241.28	8.787%	$262.4813	$262.48	$262.50	$262.50
7 purchase totals =	$951.52		$1,022.5858	$1,022.59	$1,022.60	$1,022.60