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	$222.94	5.265%	$234.6778	$234.68	$234.70	$234.70
Purchase #2	$33.81	9.544%	$37.0368	$37.04	$37.05	$37.00
Purchase #3	$76.72	11.476%	$85.5244	$85.52	$85.50	$85.50
Purchase #4	$47.94	9.523%	$52.5053	$52.51	$52.50	$52.50
Purchase #5	$190.49	13.536%	$216.2747	$216.27	$216.25	$216.30
Purchase #6	$155.92	5.300%	$164.1838	$164.18	$164.20	$164.20
Purchase #7	$36.30	6.623%	$38.7041	$38.70	$38.70	$38.70
7 purchase totals =	$764.12		$828.9069	$828.90	$828.90	$828.90