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	$133.90	3.745%	$138.9146	$138.91	$138.90	$138.90
Purchase #2	$144.82	4.535%	$151.3876	$151.39	$151.40	$151.40
Purchase #3	$226.26	11.756%	$252.8591	$252.86	$252.85	$252.90
Purchase #4	$24.56	3.653%	$25.4572	$25.46	$25.45	$25.50
Purchase #5	$59.92	9.132%	$65.3919	$65.39	$65.40	$65.40
Purchase #6	$104.26	13.592%	$118.431	$118.43	$118.45	$118.40
Purchase #7	$116.94	5.646%	$123.5424	$123.54	$123.55	$123.50
7 purchase totals =	$810.66		$875.9838	$875.98	$876.00	$876.00