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	$116.54	13.301%	$132.041	$132.04	$132.05	$132.00
Purchase #2	$188.29	13.662%	$214.0142	$214.01	$214.00	$214.00
Purchase #3	$32.90	12.508%	$37.0151	$37.02	$37.00	$37.00
Purchase #4	$36.78	9.567%	$40.2987	$40.30	$40.30	$40.30
Purchase #5	$245.36	7.230%	$263.0995	$263.10	$263.10	$263.10
Purchase #6	$177.89	12.636%	$200.3682	$200.37	$200.35	$200.40
Purchase #7	$215.58	4.675%	$225.6584	$225.66	$225.65	$225.70
7 purchase totals =	$1,013.34		$1,112.4951	$1,112.50	$1,112.45	$1,112.50