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	$158.32	9.441%	$173.267	$173.27	$173.25	$173.30
Purchase #2	$43.48	3.866%	$45.1609	$45.16	$45.15	$45.20
Purchase #3	$166.89	11.811%	$186.6014	$186.60	$186.60	$186.60
Purchase #4	$226.77	10.788%	$251.2339	$251.23	$251.25	$251.20
Purchase #5	$241.91	5.322%	$254.7845	$254.78	$254.80	$254.80
Purchase #6	$56.26	9.478%	$61.5923	$61.59	$61.60	$61.60
Purchase #7	$100.93	12.503%	$113.5493	$113.55	$113.55	$113.50
7 purchase totals =	$994.56		$1,086.1893	$1,086.18	$1,086.20	$1,086.20