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 $95.84   8.523%   $104.0084   $104.01   $104.00   $104.00  
  Purchase #2 $11.34   4.594%   $11.861   $11.86   $11.85   $11.90  
  Purchase #3 $186.35   11.605%   $207.9759   $207.98   $208.00   $208.00  
  Purchase #4 $166.99   8.719%   $181.5499   $181.55   $181.55   $181.50  
  Purchase #5 $164.56   12.386%   $184.9424   $184.94   $184.95   $184.90  
  Purchase #6 $240.29   6.458%   $255.8079   $255.81   $255.80   $255.80  
  Purchase #7 $235.28   5.224%   $247.571   $247.57   $247.55   $247.60  
  7 purchase totals = $1,100.65       $1,193.7165   $1,193.72   $1,193.70   $1,193.70