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 $151.66   10.104%   $166.9837   $166.98   $167.00   $167.00  
  Purchase #2 $225.51   9.641%   $247.2514   $247.25   $247.25   $247.30  
  Purchase #3 $58.43   13.732%   $66.4536   $66.45   $66.45   $66.50  
  Purchase #4 $40.90   9.329%   $44.7156   $44.72   $44.70   $44.70  
  Purchase #5 $66.47   13.633%   $75.5319   $75.53   $75.55   $75.50  
  Purchase #6 $229.50   5.826%   $242.8707   $242.87   $242.85   $242.90  
  Purchase #7 $162.94   11.803%   $182.1718   $182.17   $182.15   $182.20  
  7 purchase totals = $935.41       $1,025.9787   $1,025.97   $1,025.95   $1,026.10