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	$113.47	12.151%	$127.2577	$127.26	$127.25	$127.30
Purchase #2	$77.67	9.651%	$85.1659	$85.17	$85.15	$85.20
Purchase #3	$29.70	11.867%	$33.2245	$33.22	$33.20	$33.20
Purchase #4	$136.44	6.401%	$145.1735	$145.17	$145.15	$145.20
Purchase #5	$92.69	8.517%	$100.5844	$100.58	$100.60	$100.60
Purchase #6	$210.50	3.212%	$217.2613	$217.26	$217.25	$217.30
Purchase #7	$53.81	9.402%	$58.8692	$58.87	$58.85	$58.90
7 purchase totals =	$714.28		$767.5365	$767.53	$767.45	$767.70