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	$181.66	12.680%	$204.6945	$204.69	$204.70	$204.70
Purchase #2	$167.37	7.302%	$179.5914	$179.59	$179.60	$179.60
Purchase #3	$159.58	8.728%	$173.5081	$173.51	$173.50	$173.50
Purchase #4	$35.93	5.491%	$37.9029	$37.90	$37.90	$37.90
Purchase #5	$59.88	8.380%	$64.8979	$64.90	$64.90	$64.90
Purchase #6	$150.89	9.218%	$164.799	$164.80	$164.80	$164.80
Purchase #7	$41.66	7.783%	$44.9024	$44.90	$44.90	$44.90
7 purchase totals =	$796.97		$870.2962	$870.29	$870.30	$870.30