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	$9.67	13.179%	$10.9444	$10.94	$10.95	$10.90
Purchase #2	$122.51	11.734%	$136.8853	$136.89	$136.90	$136.90
Purchase #3	$162.26	10.329%	$179.0198	$179.02	$179.00	$179.00
Purchase #4	$200.93	7.743%	$216.488	$216.49	$216.50	$216.50
Purchase #5	$168.35	3.480%	$174.2086	$174.21	$174.20	$174.20
Purchase #6	$52.30	6.759%	$55.835	$55.84	$55.85	$55.80
Purchase #7	$204.33	9.435%	$223.6085	$223.61	$223.60	$223.60
7 purchase totals =	$920.35		$996.9896	$997.00	$997.00	$996.90