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	$23.93	4.498%	$25.0064	$25.01	$25.00	$25.00
Purchase #2	$83.96	13.752%	$95.5062	$95.51	$95.50	$95.50
Purchase #3	$141.60	4.781%	$148.3699	$148.37	$148.35	$148.40
Purchase #4	$195.83	10.278%	$215.9574	$215.96	$215.95	$216.00
Purchase #5	$67.43	7.449%	$72.4529	$72.45	$72.45	$72.50
Purchase #6	$87.92	13.377%	$99.6811	$99.68	$99.70	$99.70
Purchase #7	$192.89	9.476%	$211.1683	$211.17	$211.15	$211.20
7 purchase totals =	$793.56		$868.1422	$868.15	$868.10	$868.30