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	$95.72	6.431%	$101.8758	$101.88	$101.90	$101.90
Purchase #2	$40.94	10.498%	$45.2379	$45.24	$45.25	$45.20
Purchase #3	$72.78	7.549%	$78.2742	$78.27	$78.25	$78.30
Purchase #4	$82.41	5.572%	$87.0019	$87.00	$87.00	$87.00
Purchase #5	$94.87	8.788%	$103.2072	$103.21	$103.20	$103.20
Purchase #6	$68.83	5.486%	$72.606	$72.61	$72.60	$72.60
Purchase #7	$237.38	6.189%	$252.0714	$252.07	$252.05	$252.10
7 purchase totals =	$692.93		$740.2744	$740.28	$740.25	$740.30