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 $72.44   5.208%   $76.2127   $76.21   $76.20   $76.20  
  Purchase #2 $242.29   8.425%   $262.7029   $262.70   $262.70   $262.70  
  Purchase #3 $61.71   3.499%   $63.8692   $63.87   $63.85   $63.90  
  Purchase #4 $58.92   13.790%   $67.0451   $67.05   $67.05   $67.00  
  Purchase #5 $119.70   4.411%   $124.98   $124.98   $125.00   $125.00  
  Purchase #6 $169.46   9.154%   $184.9724   $184.97   $184.95   $185.00  
  Purchase #7 $202.79   12.516%   $228.1712   $228.17   $228.15   $228.20  
  7 purchase totals = $927.31       $1,007.9535   $1,007.95   $1,007.90   $1,008.00