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	$171.59	13.394%	$194.5728	$194.57	$194.55	$194.60
Purchase #2	$127.72	6.712%	$136.2926	$136.29	$136.30	$136.30
Purchase #3	$37.25	12.525%	$41.9156	$41.92	$41.90	$41.90
Purchase #4	$164.41	10.353%	$181.4314	$181.43	$181.45	$181.40
Purchase #5	$91.93	10.230%	$101.3344	$101.33	$101.35	$101.30
Purchase #6	$32.69	4.139%	$34.043	$34.04	$34.05	$34.00
Purchase #7	$161.92	6.553%	$172.5306	$172.53	$172.55	$172.50
7 purchase totals =	$787.51		$862.1204	$862.11	$862.15	$862.00