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	$192.98	12.577%	$217.2511	$217.25	$217.25	$217.30
Purchase #2	$216.86	11.198%	$241.144	$241.14	$241.15	$241.10
Purchase #3	$216.42	11.312%	$240.9014	$240.90	$240.90	$240.90
Purchase #4	$248.43	10.205%	$273.7823	$273.78	$273.80	$273.80
Purchase #5	$48.37	3.169%	$49.9028	$49.90	$49.90	$49.90
Purchase #6	$216.78	8.371%	$234.9267	$234.93	$234.95	$234.90
Purchase #7	$50.31	12.335%	$56.5157	$56.52	$56.50	$56.50
7 purchase totals =	$1,190.15		$1,314.4240	$1,314.42	$1,314.45	$1,314.40