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	$22.44	11.168%	$24.9461	$24.95	$24.95	$24.90
Purchase #2	$210.32	12.851%	$237.3482	$237.35	$237.35	$237.30
Purchase #3	$87.39	3.652%	$90.5815	$90.58	$90.60	$90.60
Purchase #4	$118.54	11.329%	$131.9694	$131.97	$131.95	$132.00
Purchase #5	$205.41	12.342%	$230.7617	$230.76	$230.75	$230.80
Purchase #6	$151.30	10.778%	$167.6071	$167.61	$167.60	$167.60
Purchase #7	$199.31	8.846%	$216.941	$216.94	$216.95	$216.90
7 purchase totals =	$994.71		$1,100.1550	$1,100.16	$1,100.15	$1,100.10