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 $193.92   4.141%   $201.9502   $201.95   $201.95   $202.00  
  Purchase #2 $14.47   13.276%   $16.391   $16.39   $16.40   $16.40  
  Purchase #3 $235.70   8.252%   $255.15   $255.15   $255.15   $255.20  
  Purchase #4 $61.28   8.645%   $66.5777   $66.58   $66.60   $66.60  
  Purchase #5 $239.28   7.507%   $257.2427   $257.24   $257.25   $257.20  
  Purchase #6 $168.39   4.430%   $175.8497   $175.85   $175.85   $175.80  
  Purchase #7 $133.55   6.691%   $142.4858   $142.49   $142.50   $142.50  
  7 purchase totals = $1,046.59       $1,115.6471   $1,115.65   $1,115.70   $1,115.70