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 $23.76   9.377%   $25.988   $25.99   $26.00   $26.00  
  Purchase #2 $184.64   12.469%   $207.6628   $207.66   $207.65   $207.70  
  Purchase #3 $164.37   9.362%   $179.7583   $179.76   $179.75   $179.80  
  Purchase #4 $42.52   5.628%   $44.913   $44.91   $44.90   $44.90  
  Purchase #5 $105.65   12.626%   $118.9894   $118.99   $119.00   $119.00  
  Purchase #6 $213.49   5.701%   $225.6611   $225.66   $225.65   $225.70  
  Purchase #7 $69.73   3.360%   $72.0729   $72.07   $72.05   $72.10  
  7 purchase totals = $804.16       $875.0455   $875.04   $875.00   $875.20