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 $57.57   7.731%   $62.0207   $62.02   $62.00   $62.00  
  Purchase #2 $226.57   9.754%   $248.6696   $248.67   $248.65   $248.70  
  Purchase #3 $130.79   13.315%   $148.2047   $148.20   $148.20   $148.20  
  Purchase #4 $225.78   9.147%   $246.4321   $246.43   $246.45   $246.40  
  Purchase #5 $165.99   7.270%   $178.0575   $178.06   $178.05   $178.10  
  Purchase #6 $75.32   10.151%   $82.9657   $82.97   $82.95   $83.00  
  Purchase #7 $250.37   4.202%   $260.8905   $260.89   $260.90   $260.90  
  7 purchase totals = $1,132.39       $1,227.2408   $1,227.24   $1,227.20   $1,227.30