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	$81.61	10.872%	$90.4826	$90.48	$90.50	$90.50
Purchase #2	$9.92	4.711%	$10.3873	$10.39	$10.40	$10.40
Purchase #3	$88.32	8.863%	$96.1478	$96.15	$96.15	$96.10
Purchase #4	$27.41	13.369%	$31.0744	$31.07	$31.05	$31.10
Purchase #5	$122.94	7.867%	$132.6117	$132.61	$132.60	$132.60
Purchase #6	$164.61	12.588%	$185.3311	$185.33	$185.35	$185.30
Purchase #7	$240.68	4.441%	$251.3686	$251.37	$251.35	$251.40
7 purchase totals =	$735.49		$797.4035	$797.40	$797.40	$797.40