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 $151.96   6.249%   $161.456   $161.46   $161.45   $161.50  
  Purchase #2 $35.78   3.788%   $37.1353   $37.14   $37.15   $37.10  
  Purchase #3 $160.63   11.474%   $179.0607   $179.06   $179.05   $179.10  
  Purchase #4 $144.66   12.718%   $163.0579   $163.06   $163.05   $163.10  
  Purchase #5 $210.28   3.753%   $218.1718   $218.17   $218.15   $218.20  
  Purchase #6 $211.92   12.330%   $238.0497   $238.05   $238.05   $238.00  
  Purchase #7 $26.48   11.730%   $29.5861   $29.59   $29.60   $29.60  
  7 purchase totals = $941.71       $1,026.5175   $1,026.53   $1,026.50   $1,026.60