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 $214.39   8.327%   $232.2423   $232.24   $232.25   $232.20  
  Purchase #2 $128.51   12.731%   $144.8706   $144.87   $144.85   $144.90  
  Purchase #3 $23.46   9.533%   $25.6964   $25.70   $25.70   $25.70  
  Purchase #4 $58.76   10.765%   $65.0855   $65.09   $65.10   $65.10  
  Purchase #5 $186.76   7.854%   $201.4281   $201.43   $201.45   $201.40  
  Purchase #6 $148.27   7.672%   $159.6453   $159.65   $159.65   $159.60  
  Purchase #7 $203.37   5.425%   $214.4028   $214.40   $214.40   $214.40  
  7 purchase totals = $963.52       $1,043.3710   $1,043.38   $1,043.40   $1,043.30