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	$49.54	8.635%	$53.8178	$53.82	$53.80	$53.80
Purchase #2	$217.83	12.431%	$244.9084	$244.91	$244.90	$244.90
Purchase #3	$180.45	5.622%	$190.5949	$190.59	$190.60	$190.60
Purchase #4	$32.27	11.205%	$35.8859	$35.89	$35.90	$35.90
Purchase #5	$89.92	9.191%	$98.1845	$98.18	$98.20	$98.20
Purchase #6	$226.27	12.479%	$254.5062	$254.51	$254.50	$254.50
Purchase #7	$188.59	10.428%	$208.2562	$208.26	$208.25	$208.30
7 purchase totals =	$984.87		$1,086.1539	$1,086.16	$1,086.15	$1,086.20