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 $151.48   13.347%   $171.698   $171.70   $171.70   $171.70  
  Purchase #2 $84.69   12.169%   $94.9959   $95.00   $95.00   $95.00  
  Purchase #3 $50.82   10.774%   $56.2953   $56.30   $56.30   $56.30  
  Purchase #4 $171.47   7.342%   $184.0593   $184.06   $184.05   $184.10  
  Purchase #5 $217.31   11.366%   $242.0095   $242.01   $242.00   $242.00  
  Purchase #6 $67.31   5.774%   $71.1965   $71.20   $71.20   $71.20  
  Purchase #7 $24.94   4.452%   $26.0503   $26.05   $26.05   $26.10  
  7 purchase totals = $768.02       $846.3048   $846.32   $846.30   $846.40