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	$205.37	13.346%	$232.7787	$232.78	$232.80	$232.80
Purchase #2	$88.88	6.402%	$94.5701	$94.57	$94.55	$94.60
Purchase #3	$55.95	6.204%	$59.4211	$59.42	$59.40	$59.40
Purchase #4	$178.81	6.545%	$190.5131	$190.51	$190.50	$190.50
Purchase #5	$214.74	12.241%	$241.0263	$241.03	$241.05	$241.00
Purchase #6	$84.78	5.531%	$89.4692	$89.47	$89.45	$89.50
Purchase #7	$177.97	11.144%	$197.803	$197.80	$197.80	$197.80
7 purchase totals =	$1,006.50		$1,105.5815	$1,105.58	$1,105.55	$1,105.60