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 $210.80   11.463%   $234.964   $234.96   $234.95   $235.00  
  Purchase #2 $111.69   5.441%   $117.7671   $117.77   $117.75   $117.80  
  Purchase #3 $5.61   13.289%   $6.3555   $6.36   $6.35   $6.40  
  Purchase #4 $73.35   3.719%   $76.0779   $76.08   $76.10   $76.10  
  Purchase #5 $163.26   4.802%   $171.0997   $171.10   $171.10   $171.10  
  Purchase #6 $67.58   7.535%   $72.6722   $72.67   $72.65   $72.70  
  Purchase #7 $70.73   7.540%   $76.063   $76.06   $76.05   $76.10  
  7 purchase totals = $703.02       $754.9994   $755.00   $754.95   $755.20