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	$203.55	4.747%	$213.2125	$213.21	$213.20	$213.20
Purchase #2	$22.98	6.818%	$24.5468	$24.55	$24.55	$24.50
Purchase #3	$227.93	9.847%	$250.3743	$250.37	$250.35	$250.40
Purchase #4	$215.42	4.423%	$224.948	$224.95	$224.95	$224.90
Purchase #5	$6.75	3.321%	$6.9742	$6.97	$6.95	$7.00
Purchase #6	$138.33	10.308%	$152.5891	$152.59	$152.60	$152.60
Purchase #7	$72.86	8.263%	$78.8804	$78.88	$78.90	$78.90
7 purchase totals =	$887.82		$951.5253	$951.52	$951.50	$951.50