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	$133.82	4.141%	$139.3615	$139.36	$139.35	$139.40
Purchase #2	$72.78	5.274%	$76.6184	$76.62	$76.60	$76.60
Purchase #3	$222.50	9.635%	$243.9379	$243.94	$243.95	$243.90
Purchase #4	$219.98	3.814%	$228.37	$228.37	$228.35	$228.40
Purchase #5	$43.89	8.606%	$47.6672	$47.67	$47.65	$47.70
Purchase #6	$22.68	8.665%	$24.6452	$24.65	$24.65	$24.60
Purchase #7	$225.71	13.417%	$255.9935	$255.99	$256.00	$256.00
7 purchase totals =	$941.36		$1,016.5937	$1,016.60	$1,016.55	$1,016.60