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	$206.55	13.264%	$233.9468	$233.95	$233.95	$233.90
Purchase #2	$136.66	13.311%	$154.8508	$154.85	$154.85	$154.90
Purchase #3	$155.32	10.727%	$171.9812	$171.98	$172.00	$172.00
Purchase #4	$241.46	4.468%	$252.2484	$252.25	$252.25	$252.20
Purchase #5	$38.91	11.602%	$43.4243	$43.42	$43.40	$43.40
Purchase #6	$137.69	7.250%	$147.6725	$147.67	$147.65	$147.70
Purchase #7	$134.28	4.196%	$139.9144	$139.91	$139.90	$139.90
7 purchase totals =	$1,050.87		$1,144.0384	$1,144.03	$1,144.00	$1,144.00