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	$156.48	9.670%	$171.6116	$171.61	$171.60	$171.60
Purchase #2	$235.96	11.232%	$262.463	$262.46	$262.45	$262.50
Purchase #3	$43.58	3.313%	$45.0238	$45.02	$45.00	$45.00
Purchase #4	$135.94	5.869%	$143.9183	$143.92	$143.90	$143.90
Purchase #5	$242.58	3.286%	$250.5512	$250.55	$250.55	$250.60
Purchase #6	$192.39	6.293%	$204.4971	$204.50	$204.50	$204.50
Purchase #7	$243.31	5.410%	$256.4731	$256.47	$256.45	$256.50
7 purchase totals =	$1,250.24		$1,334.5381	$1,334.53	$1,334.45	$1,334.60