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 $168.61   3.198%   $174.0021   $174.00   $174.00   $174.00  
  Purchase #2 $41.61   13.377%   $47.1762   $47.18   $47.20   $47.20  
  Purchase #3 $144.45   3.649%   $149.721   $149.72   $149.70   $149.70  
  Purchase #4 $122.78   3.419%   $126.9778   $126.98   $127.00   $127.00  
  Purchase #5 $100.49   12.176%   $112.7257   $112.73   $112.75   $112.70  
  Purchase #6 $188.56   6.726%   $201.2425   $201.24   $201.25   $201.20  
  Purchase #7 $188.27   5.649%   $198.9054   $198.91   $198.90   $198.90  
  7 purchase totals = $954.77       $1,010.7507   $1,010.76   $1,010.80   $1,010.70