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 $188.45   7.550%   $202.678   $202.68   $202.70   $202.70  
  Purchase #2 $212.66   5.782%   $224.956   $224.96   $224.95   $225.00  
  Purchase #3 $125.86   9.498%   $137.8142   $137.81   $137.80   $137.80  
  Purchase #4 $234.87   6.309%   $249.6879   $249.69   $249.70   $249.70  
  Purchase #5 $104.75   9.495%   $114.696   $114.70   $114.70   $114.70  
  Purchase #6 $26.72   5.634%   $28.2254   $28.23   $28.25   $28.20  
  Purchase #7 $110.90   5.674%   $117.1925   $117.19   $117.20   $117.20  
  7 purchase totals = $1,004.21       $1,075.2500   $1,075.26   $1,075.30   $1,075.30