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	$163.52	6.545%	$174.2224	$174.22	$174.20	$174.20
Purchase #2	$72.96	13.358%	$82.706	$82.71	$82.70	$82.70
Purchase #3	$76.87	6.661%	$81.9903	$81.99	$82.00	$82.00
Purchase #4	$39.81	5.577%	$42.0302	$42.03	$42.05	$42.00
Purchase #5	$246.30	13.436%	$279.3929	$279.39	$279.40	$279.40
Purchase #6	$113.28	8.565%	$122.9824	$122.98	$123.00	$123.00
Purchase #7	$220.45	6.550%	$234.8895	$234.89	$234.90	$234.90
7 purchase totals =	$933.19		$1,018.2137	$1,018.21	$1,018.25	$1,018.20