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 $84.53   12.405%   $95.0159   $95.02   $95.00   $95.00  
  Purchase #2 $235.84   5.138%   $247.9575   $247.96   $247.95   $248.00  
  Purchase #3 $88.63   6.520%   $94.4087   $94.41   $94.40   $94.40  
  Purchase #4 $242.53   4.661%   $253.8343   $253.83   $253.85   $253.80  
  Purchase #5 $123.87   11.178%   $137.7162   $137.72   $137.70   $137.70  
  Purchase #6 $200.92   4.401%   $209.7625   $209.76   $209.75   $209.80  
  Purchase #7 $64.42   13.306%   $72.9917   $72.99   $73.00   $73.00  
  7 purchase totals = $1,040.74       $1,111.6868   $1,111.69   $1,111.65   $1,111.70