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	$114.94	10.807%	$127.3616	$127.36	$127.35	$127.40
Purchase #2	$11.89	3.476%	$12.3033	$12.30	$12.30	$12.30
Purchase #3	$46.26	4.341%	$48.2681	$48.27	$48.25	$48.30
Purchase #4	$172.59	3.435%	$178.5185	$178.52	$178.50	$178.50
Purchase #5	$89.70	13.549%	$101.8535	$101.85	$101.85	$101.90
Purchase #6	$141.91	6.827%	$151.5982	$151.60	$151.60	$151.60
Purchase #7	$179.79	5.314%	$189.344	$189.34	$189.35	$189.30
7 purchase totals =	$757.08		$809.2472	$809.24	$809.20	$809.30