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	$140.61	8.172%	$152.1006	$152.10	$152.10	$152.10
Purchase #2	$87.67	11.720%	$97.9449	$97.94	$97.95	$97.90
Purchase #3	$117.29	8.478%	$127.2338	$127.23	$127.25	$127.20
Purchase #4	$133.55	9.661%	$146.4523	$146.45	$146.45	$146.50
Purchase #5	$125.68	8.555%	$136.4319	$136.43	$136.45	$136.40
Purchase #6	$55.88	11.220%	$62.1497	$62.15	$62.15	$62.10
Purchase #7	$143.46	10.783%	$158.9293	$158.93	$158.95	$158.90
7 purchase totals =	$804.14		$881.2425	$881.23	$881.30	$881.10