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 $44.74   5.806%   $47.3376   $47.34   $47.35   $47.30  
  Purchase #2 $218.49   8.187%   $236.3778   $236.38   $236.40   $236.40  
  Purchase #3 $157.86   6.425%   $168.0025   $168.00   $168.00   $168.00  
  Purchase #4 $229.87   13.461%   $260.8128   $260.81   $260.80   $260.80  
  Purchase #5 $233.41   13.837%   $265.7069   $265.71   $265.70   $265.70  
  Purchase #6 $102.45   9.602%   $112.2872   $112.29   $112.30   $112.30  
  Purchase #7 $9.70   13.577%   $11.017   $11.02   $11.00   $11.00  
  7 purchase totals = $996.52       $1,101.5418   $1,101.55   $1,101.55   $1,101.50