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	$229.36	13.762%	$260.9245	$260.92	$260.90	$260.90
Purchase #2	$92.46	8.564%	$100.3783	$100.38	$100.40	$100.40
Purchase #3	$85.90	3.189%	$88.6394	$88.64	$88.65	$88.60
Purchase #4	$211.97	7.795%	$228.4931	$228.49	$228.50	$228.50
Purchase #5	$174.65	12.685%	$196.8044	$196.80	$196.80	$196.80
Purchase #6	$109.83	9.149%	$119.8783	$119.88	$119.90	$119.90
Purchase #7	$141.34	3.705%	$146.5766	$146.58	$146.60	$146.60
7 purchase totals =	$1,045.51		$1,141.6946	$1,141.69	$1,141.75	$1,141.70