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 $90.83   5.262%   $95.6095   $95.61   $95.60   $95.60  
  Purchase #2 $134.74   5.775%   $142.5212   $142.52   $142.50   $142.50  
  Purchase #3 $32.57   11.276%   $36.2426   $36.24   $36.25   $36.20  
  Purchase #4 $125.94   8.565%   $136.7268   $136.73   $136.75   $136.70  
  Purchase #5 $201.82   5.383%   $212.684   $212.68   $212.70   $212.70  
  Purchase #6 $167.85   6.709%   $179.1111   $179.11   $179.10   $179.10  
  Purchase #7 $181.71   4.411%   $189.7252   $189.73   $189.75   $189.70  
  7 purchase totals = $935.46       $992.6204   $992.62   $992.65   $992.50