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 $194.69   6.148%   $206.6595   $206.66   $206.65   $206.70  
  Purchase #2 $238.26   10.151%   $262.4458   $262.45   $262.45   $262.40  
  Purchase #3 $51.53   10.154%   $56.7624   $56.76   $56.75   $56.80  
  Purchase #4 $218.67   7.215%   $234.447   $234.45   $234.45   $234.40  
  Purchase #5 $25.51   3.807%   $26.4812   $26.48   $26.50   $26.50  
  Purchase #6 $189.50   9.312%   $207.1462   $207.15   $207.15   $207.10  
  Purchase #7 $92.90   10.323%   $102.4901   $102.49   $102.50   $102.50  
  7 purchase totals = $1,011.06       $1,096.4322   $1,096.44   $1,096.45   $1,096.40