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	$205.89	7.632%	$221.6035	$221.60	$221.60	$221.60
Purchase #2	$43.89	10.345%	$48.4304	$48.43	$48.45	$48.40
Purchase #3	$233.31	12.386%	$262.2078	$262.21	$262.20	$262.20
Purchase #4	$113.69	10.401%	$125.5149	$125.51	$125.50	$125.50
Purchase #5	$98.92	6.342%	$105.1935	$105.19	$105.20	$105.20
Purchase #6	$127.99	7.390%	$137.4485	$137.45	$137.45	$137.40
Purchase #7	$195.65	6.729%	$208.8153	$208.82	$208.80	$208.80
7 purchase totals =	$1,019.34		$1,109.2139	$1,109.21	$1,109.20	$1,109.10