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 $164.97   6.321%   $175.3978   $175.40   $175.40   $175.40  
  Purchase #2 $157.83   3.611%   $163.5292   $163.53   $163.55   $163.50  
  Purchase #3 $84.99   11.389%   $94.6695   $94.67   $94.65   $94.70  
  Purchase #4 $61.80   7.558%   $66.4708   $66.47   $66.45   $66.50  
  Purchase #5 $246.92   7.199%   $264.6958   $264.70   $264.70   $264.70  
  Purchase #6 $65.81   13.756%   $74.8628   $74.86   $74.85   $74.90  
  Purchase #7 $235.37   8.726%   $255.9084   $255.91   $255.90   $255.90  
  7 purchase totals = $1,017.69       $1,095.5343   $1,095.54   $1,095.50   $1,095.60