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	$112.93	4.829%	$118.3834	$118.38	$118.40	$118.40
Purchase #2	$21.84	3.446%	$22.5926	$22.59	$22.60	$22.60
Purchase #3	$73.25	5.584%	$77.3403	$77.34	$77.35	$77.30
Purchase #4	$41.68	9.167%	$45.5008	$45.50	$45.50	$45.50
Purchase #5	$102.36	8.718%	$111.2837	$111.28	$111.30	$111.30
Purchase #6	$48.42	10.134%	$53.3269	$53.33	$53.35	$53.30
Purchase #7	$186.54	11.825%	$208.5984	$208.60	$208.60	$208.60
7 purchase totals =	$587.02		$637.0261	$637.02	$637.10	$637.00