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	$59.53	13.664%	$67.6642	$67.66	$67.65	$67.70
Purchase #2	$63.91	6.294%	$67.9325	$67.93	$67.95	$67.90
Purchase #3	$45.76	5.107%	$48.097	$48.10	$48.10	$48.10
Purchase #4	$229.71	11.209%	$255.4582	$255.46	$255.45	$255.50
Purchase #5	$37.29	12.638%	$42.0027	$42.00	$42.00	$42.00
Purchase #6	$246.74	10.471%	$272.5761	$272.58	$272.60	$272.60
Purchase #7	$139.88	13.629%	$158.9442	$158.94	$158.95	$158.90
7 purchase totals =	$822.82		$912.6749	$912.67	$912.70	$912.70