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	$134.28	8.476%	$145.6616	$145.66	$145.65	$145.70
Purchase #2	$118.73	5.490%	$125.2483	$125.25	$125.25	$125.20
Purchase #3	$131.94	9.359%	$144.2883	$144.29	$144.30	$144.30
Purchase #4	$156.25	5.517%	$164.8703	$164.87	$164.85	$164.90
Purchase #5	$132.82	13.194%	$150.3443	$150.34	$150.35	$150.30
Purchase #6	$63.39	11.541%	$70.7058	$70.71	$70.70	$70.70
Purchase #7	$98.94	13.604%	$112.3998	$112.40	$112.40	$112.40
7 purchase totals =	$836.35		$913.5184	$913.52	$913.50	$913.50