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	$76.72	13.730%	$87.2537	$87.25	$87.25	$87.30
Purchase #2	$98.50	13.204%	$111.5059	$111.51	$111.50	$111.50
Purchase #3	$247.85	9.853%	$272.2707	$272.27	$272.25	$272.30
Purchase #4	$21.54	12.569%	$24.2474	$24.25	$24.25	$24.20
Purchase #5	$37.79	11.770%	$42.2379	$42.24	$42.25	$42.20
Purchase #6	$226.44	7.534%	$243.5	$243.50	$243.50	$243.50
Purchase #7	$138.98	6.479%	$147.9845	$147.98	$148.00	$148.00
7 purchase totals =	$847.82		$929.0001	$929.00	$929.00	$929.00