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 $97.27   13.870%   $110.7613   $110.76   $110.75   $110.80  
  Purchase #2 $80.80   13.492%   $91.7015   $91.70   $91.70   $91.70  
  Purchase #3 $208.65   3.361%   $215.6627   $215.66   $215.65   $215.70  
  Purchase #4 $195.89   9.202%   $213.9158   $213.92   $213.90   $213.90  
  Purchase #5 $58.80   5.447%   $62.0028   $62.00   $62.00   $62.00  
  Purchase #6 $75.41   11.280%   $83.9162   $83.92   $83.90   $83.90  
  Purchase #7 $230.59   3.102%   $237.7429   $237.74   $237.75   $237.70  
  7 purchase totals = $947.41       $1,015.7032   $1,015.70   $1,015.65   $1,015.70