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	$104.54	11.658%	$116.7273	$116.73	$116.75	$116.70
Purchase #2	$53.60	7.738%	$57.7476	$57.75	$57.75	$57.70
Purchase #3	$246.34	10.216%	$271.5061	$271.51	$271.50	$271.50
Purchase #4	$235.44	11.673%	$262.9229	$262.92	$262.90	$262.90
Purchase #5	$191.35	7.443%	$205.5922	$205.59	$205.60	$205.60
Purchase #6	$9.66	13.406%	$10.955	$10.96	$10.95	$11.00
Purchase #7	$38.52	10.276%	$42.4783	$42.48	$42.50	$42.50
7 purchase totals =	$879.45		$967.9294	$967.94	$967.95	$967.90