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 $33.59   6.312%   $35.7102   $35.71   $35.70   $35.70  
  Purchase #2 $88.92   9.763%   $97.6013   $97.60   $97.60   $97.60  
  Purchase #3 $216.56   3.459%   $224.0508   $224.05   $224.05   $224.10  
  Purchase #4 $112.86   9.297%   $123.3526   $123.35   $123.35   $123.40  
  Purchase #5 $239.48   4.266%   $249.6962   $249.70   $249.70   $249.70  
  Purchase #6 $232.72   10.776%   $257.7979   $257.80   $257.80   $257.80  
  Purchase #7 $243.91   4.829%   $255.6884   $255.69   $255.70   $255.70  
  7 purchase totals = $1,168.04       $1,243.8974   $1,243.90   $1,243.90   $1,244.00