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	$216.83	13.622%	$246.3666	$246.37	$246.35	$246.40
Purchase #2	$36.31	11.574%	$40.5125	$40.51	$40.50	$40.50
Purchase #3	$123.45	3.727%	$128.051	$128.05	$128.05	$128.10
Purchase #4	$203.30	5.507%	$214.4957	$214.50	$214.50	$214.50
Purchase #5	$196.66	4.483%	$205.4763	$205.48	$205.50	$205.50
Purchase #6	$52.92	5.617%	$55.8925	$55.89	$55.90	$55.90
Purchase #7	$88.40	9.665%	$96.9439	$96.94	$96.95	$96.90
7 purchase totals =	$917.87		$987.7385	$987.74	$987.75	$987.80