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 $175.58   11.522%   $195.8103   $195.81   $195.80   $195.80  
  Purchase #2 $63.89   11.289%   $71.1025   $71.10   $71.10   $71.10  
  Purchase #3 $6.46   5.372%   $6.807   $6.81   $6.80   $6.80  
  Purchase #4 $78.43   7.381%   $84.2189   $84.22   $84.20   $84.20  
  Purchase #5 $51.71   6.347%   $54.992   $54.99   $55.00   $55.00  
  Purchase #6 $246.36   5.261%   $259.321   $259.32   $259.30   $259.30  
  Purchase #7 $68.78   6.794%   $73.4529   $73.45   $73.45   $73.50  
  7 purchase totals = $691.21       $745.7046   $745.70   $745.65   $745.70