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 $216.38   7.497%   $232.602   $232.60   $232.60   $232.60  
  Purchase #2 $50.81   13.552%   $57.6958   $57.70   $57.70   $57.70  
  Purchase #3 $219.36   5.789%   $232.0588   $232.06   $232.05   $232.10  
  Purchase #4 $203.83   9.742%   $223.6871   $223.69   $223.70   $223.70  
  Purchase #5 $92.93   8.535%   $100.8616   $100.86   $100.85   $100.90  
  Purchase #6 $113.28   10.102%   $124.7235   $124.72   $124.70   $124.70  
  Purchase #7 $22.28   8.620%   $24.2005   $24.20   $24.20   $24.20  
  7 purchase totals = $918.87       $995.8293   $995.83   $995.80   $995.90