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	$135.43	7.240%	$145.2351	$145.24	$145.25	$145.20
Purchase #2	$191.35	11.822%	$213.9714	$213.97	$213.95	$214.00
Purchase #3	$114.45	11.571%	$127.693	$127.69	$127.70	$127.70
Purchase #4	$206.80	5.137%	$217.4233	$217.42	$217.40	$217.40
Purchase #5	$18.92	8.718%	$20.5694	$20.57	$20.55	$20.60
Purchase #6	$157.78	10.225%	$173.913	$173.91	$173.90	$173.90
Purchase #7	$92.77	6.598%	$98.891	$98.89	$98.90	$98.90
7 purchase totals =	$917.50		$997.6962	$997.69	$997.65	$997.70