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 $114.58   9.289%   $125.2233   $125.22   $125.20   $125.20  
  Purchase #2 $145.96   11.749%   $163.1088   $163.11   $163.10   $163.10  
  Purchase #3 $12.98   13.680%   $14.7557   $14.76   $14.75   $14.80  
  Purchase #4 $214.61   9.126%   $234.1953   $234.20   $234.20   $234.20  
  Purchase #5 $63.30   12.743%   $71.3663   $71.37   $71.35   $71.40  
  Purchase #6 $98.37   12.874%   $111.0342   $111.03   $111.05   $111.00  
  Purchase #7 $50.52   4.636%   $52.8621   $52.86   $52.85   $52.90  
  7 purchase totals = $700.32       $772.5457   $772.55   $772.50   $772.60