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	$60.87	10.756%	$67.4172	$67.42	$67.40	$67.40
Purchase #2	$89.92	13.314%	$101.8919	$101.89	$101.90	$101.90
Purchase #3	$92.53	4.745%	$96.9205	$96.92	$96.90	$96.90
Purchase #4	$184.77	12.801%	$208.4224	$208.42	$208.40	$208.40
Purchase #5	$210.49	9.725%	$230.9602	$230.96	$230.95	$231.00
Purchase #6	$16.25	13.775%	$18.4884	$18.49	$18.50	$18.50
Purchase #7	$230.75	11.151%	$256.4809	$256.48	$256.50	$256.50
7 purchase totals =	$885.58		$980.5815	$980.58	$980.55	$980.60