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	$204.43	6.160%	$217.0229	$217.02	$217.00	$217.00
Purchase #2	$21.83	12.175%	$24.4878	$24.49	$24.50	$24.50
Purchase #3	$162.32	10.417%	$179.2289	$179.23	$179.25	$179.20
Purchase #4	$46.68	12.410%	$52.473	$52.47	$52.45	$52.50
Purchase #5	$66.29	9.707%	$72.7248	$72.72	$72.70	$72.70
Purchase #6	$105.90	12.269%	$118.8929	$118.89	$118.90	$118.90
Purchase #7	$54.91	11.428%	$61.1851	$61.19	$61.20	$61.20
7 purchase totals =	$662.36		$726.0154	$726.01	$726.00	$726.00