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 $98.97   13.867%   $112.6942   $112.69   $112.70   $112.70  
  Purchase #2 $62.72   4.697%   $65.666   $65.67   $65.65   $65.70  
  Purchase #3 $24.63   11.564%   $27.4782   $27.48   $27.50   $27.50  
  Purchase #4 $209.31   9.747%   $229.7114   $229.71   $229.70   $229.70  
  Purchase #5 $123.77   13.628%   $140.6374   $140.64   $140.65   $140.60  
  Purchase #6 $24.52   4.814%   $25.7004   $25.70   $25.70   $25.70  
  Purchase #7 $85.70   9.757%   $94.0617   $94.06   $94.05   $94.10  
  7 purchase totals = $629.62       $695.9493   $695.95   $695.95   $696.00