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 $116.39   8.259%   $126.0027   $126.00   $126.00   $126.00  
  Purchase #2 $166.91   4.480%   $174.3876   $174.39   $174.40   $174.40  
  Purchase #3 $78.77   6.268%   $83.7073   $83.71   $83.70   $83.70  
  Purchase #4 $202.49   4.524%   $211.6506   $211.65   $211.65   $211.70  
  Purchase #5 $7.74   8.425%   $8.3921   $8.39   $8.40   $8.40  
  Purchase #6 $210.25   5.711%   $222.2574   $222.26   $222.25   $222.30  
  Purchase #7 $45.64   7.393%   $49.0142   $49.01   $49.00   $49.00  
  7 purchase totals = $828.19       $875.4119   $875.41   $875.40   $875.50