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 $96.52   9.619%   $105.8043   $105.80   $105.80   $105.80  
  Purchase #2 $23.70   9.706%   $26.0003   $26.00   $26.00   $26.00  
  Purchase #3 $88.66   5.376%   $93.4264   $93.43   $93.45   $93.40  
  Purchase #4 $164.93   6.469%   $175.5993   $175.60   $175.60   $175.60  
  Purchase #5 $111.32   12.647%   $125.3986   $125.40   $125.40   $125.40  
  Purchase #6 $245.51   10.541%   $271.3892   $271.39   $271.40   $271.40  
  Purchase #7 $80.63   9.654%   $88.414   $88.41   $88.40   $88.40  
  7 purchase totals = $811.27       $886.0321   $886.03   $886.05   $886.00