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 $88.58   7.459%   $95.1872   $95.19   $95.20   $95.20  
  Purchase #2 $133.84   13.370%   $151.7344   $151.73   $151.75   $151.70  
  Purchase #3 $54.33   3.247%   $56.0941   $56.09   $56.10   $56.10  
  Purchase #4 $233.87   11.230%   $260.1336   $260.13   $260.15   $260.10  
  Purchase #5 $58.75   5.554%   $62.013   $62.01   $62.00   $62.00  
  Purchase #6 $90.81   12.122%   $101.818   $101.82   $101.80   $101.80  
  Purchase #7 $205.73   7.423%   $221.0013   $221.00   $221.00   $221.00  
  7 purchase totals = $865.91       $947.9816   $947.97   $948.00   $947.90