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 $59.37   6.435%   $63.1905   $63.19   $63.20   $63.20  
  Purchase #2 $245.87   11.635%   $274.477   $274.48   $274.50   $274.50  
  Purchase #3 $93.90   10.650%   $103.9004   $103.90   $103.90   $103.90  
  Purchase #4 $221.80   6.618%   $236.4787   $236.48   $236.50   $236.50  
  Purchase #5 $221.35   11.215%   $246.1744   $246.17   $246.15   $246.20  
  Purchase #6 $106.91   13.554%   $121.4006   $121.40   $121.40   $121.40  
  Purchase #7 $89.36   6.861%   $95.491   $95.49   $95.50   $95.50  
  7 purchase totals = $1,038.56       $1,141.1126   $1,141.11   $1,141.15   $1,141.20