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 $62.97   6.296%   $66.9346   $66.93   $66.95   $66.90  
  Purchase #2 $211.60   7.260%   $226.9622   $226.96   $226.95   $227.00  
  Purchase #3 $31.78   5.295%   $33.4628   $33.46   $33.45   $33.50  
  Purchase #4 $86.53   13.150%   $97.9087   $97.91   $97.90   $97.90  
  Purchase #5 $27.96   9.110%   $30.5072   $30.51   $30.50   $30.50  
  Purchase #6 $56.56   3.706%   $58.6561   $58.66   $58.65   $58.70  
  Purchase #7 $238.58   3.663%   $247.3192   $247.32   $247.30   $247.30  
  7 purchase totals = $715.98       $761.7508   $761.75   $761.70   $761.80