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	$218.71	11.204%	$243.2143	$243.21	$243.20	$243.20
Purchase #2	$243.57	9.845%	$267.5495	$267.55	$267.55	$267.50
Purchase #3	$89.47	3.378%	$92.4923	$92.49	$92.50	$92.50
Purchase #4	$108.39	3.157%	$111.8119	$111.81	$111.80	$111.80
Purchase #5	$48.56	10.134%	$53.4811	$53.48	$53.50	$53.50
Purchase #6	$163.86	7.509%	$176.1642	$176.16	$176.15	$176.20
Purchase #7	$95.36	3.361%	$98.565	$98.57	$98.55	$98.60
7 purchase totals =	$967.92		$1,043.2783	$1,043.27	$1,043.25	$1,043.30