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	$158.89	3.535%	$164.5068	$164.51	$164.50	$164.50
Purchase #2	$152.99	8.668%	$166.2512	$166.25	$166.25	$166.30
Purchase #3	$12.29	7.856%	$13.2555	$13.26	$13.25	$13.30
Purchase #4	$206.66	3.498%	$213.889	$213.89	$213.90	$213.90
Purchase #5	$114.25	9.284%	$124.857	$124.86	$124.85	$124.90
Purchase #6	$173.29	11.356%	$192.9688	$192.97	$192.95	$193.00
Purchase #7	$147.57	11.759%	$164.9228	$164.92	$164.90	$164.90
7 purchase totals =	$965.94		$1,040.6511	$1,040.66	$1,040.60	$1,040.80