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 $119.87   3.407%   $123.954   $123.95   $123.95   $124.00  
  Purchase #2 $38.60   11.267%   $42.9491   $42.95   $42.95   $42.90  
  Purchase #3 $223.34   8.462%   $242.239   $242.24   $242.25   $242.20  
  Purchase #4 $175.90   13.829%   $200.2252   $200.23   $200.25   $200.20  
  Purchase #5 $15.25   11.825%   $17.0533   $17.05   $17.05   $17.10  
  Purchase #6 $35.47   12.332%   $39.8442   $39.84   $39.85   $39.80  
  Purchase #7 $34.74   8.591%   $37.7245   $37.72   $37.70   $37.70  
  7 purchase totals = $643.17       $703.9893   $703.98   $704.00   $703.90