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	$179.79	5.273%	$189.2703	$189.27	$189.25	$189.30
Purchase #2	$45.67	3.563%	$47.2972	$47.30	$47.30	$47.30
Purchase #3	$57.99	6.719%	$61.8863	$61.89	$61.90	$61.90
Purchase #4	$210.41	12.189%	$236.0569	$236.06	$236.05	$236.10
Purchase #5	$176.75	11.134%	$196.4293	$196.43	$196.45	$196.40
Purchase #6	$215.47	10.838%	$238.8226	$238.82	$238.80	$238.80
Purchase #7	$246.69	10.496%	$272.5826	$272.58	$272.60	$272.60
7 purchase totals =	$1,132.77		$1,242.3452	$1,242.35	$1,242.35	$1,242.40