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 $23.87   11.322%   $26.5726   $26.57   $26.55   $26.60  
  Purchase #2 $158.78   3.135%   $163.7578   $163.76   $163.75   $163.80  
  Purchase #3 $12.62   8.616%   $13.7073   $13.71   $13.70   $13.70  
  Purchase #4 $148.62   11.437%   $165.6177   $165.62   $165.60   $165.60  
  Purchase #5 $202.61   7.604%   $218.0165   $218.02   $218.00   $218.00  
  Purchase #6 $198.84   6.624%   $212.0112   $212.01   $212.00   $212.00  
  Purchase #7 $126.97   11.595%   $141.6922   $141.69   $141.70   $141.70  
  7 purchase totals = $872.31       $941.3753   $941.38   $941.30   $941.40