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 $69.71   7.600%   $75.008   $75.01   $75.00   $75.00  
  Purchase #2 $205.48   13.428%   $233.0719   $233.07   $233.05   $233.10  
  Purchase #3 $69.30   12.698%   $78.0997   $78.10   $78.10   $78.10  
  Purchase #4 $221.98   4.445%   $231.847   $231.85   $231.85   $231.80  
  Purchase #5 $238.25   9.630%   $261.1935   $261.19   $261.20   $261.20  
  Purchase #6 $152.57   9.245%   $166.6751   $166.68   $166.70   $166.70  
  Purchase #7 $59.71   11.684%   $66.6865   $66.69   $66.70   $66.70  
  7 purchase totals = $1,017.00       $1,112.5817   $1,112.59   $1,112.60   $1,112.60