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	$6.87	5.270%	$7.232	$7.23	$7.25	$7.20
Purchase #2	$39.44	10.466%	$43.5678	$43.57	$43.55	$43.60
Purchase #3	$6.90	11.509%	$7.6941	$7.69	$7.70	$7.70
Purchase #4	$72.93	12.509%	$82.0528	$82.05	$82.05	$82.10
Purchase #5	$98.66	13.209%	$111.692	$111.69	$111.70	$111.70
Purchase #6	$58.35	10.540%	$64.5001	$64.50	$64.50	$64.50
Purchase #7	$218.70	13.174%	$247.5115	$247.51	$247.50	$247.50
7 purchase totals =	$501.85		$564.2503	$564.24	$564.25	$564.30