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 $201.54   8.684%   $219.0417   $219.04   $219.05   $219.00  
  Purchase #2 $246.87   6.275%   $262.3611   $262.36   $262.35   $262.40  
  Purchase #3 $79.27   3.366%   $81.9382   $81.94   $81.95   $81.90  
  Purchase #4 $76.70   13.235%   $86.8512   $86.85   $86.85   $86.90  
  Purchase #5 $29.77   11.454%   $33.1799   $33.18   $33.20   $33.20  
  Purchase #6 $224.93   3.366%   $232.5011   $232.50   $232.50   $232.50  
  Purchase #7 $175.26   4.226%   $182.6665   $182.67   $182.65   $182.70  
  7 purchase totals = $1,034.34       $1,098.5397   $1,098.54   $1,098.55   $1,098.60