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 $208.59   4.183%   $217.3153   $217.32   $217.30   $217.30  
  Purchase #2 $232.89   13.554%   $264.4559   $264.46   $264.45   $264.50  
  Purchase #3 $195.67   9.194%   $213.6599   $213.66   $213.65   $213.70  
  Purchase #4 $223.65   8.552%   $242.7765   $242.78   $242.80   $242.80  
  Purchase #5 $240.42   9.689%   $263.7143   $263.71   $263.70   $263.70  
  Purchase #6 $187.90   7.856%   $202.6614   $202.66   $202.65   $202.70  
  Purchase #7 $64.86   3.648%   $67.2261   $67.23   $67.25   $67.20  
  7 purchase totals = $1,353.98       $1,471.8094   $1,471.82   $1,471.80   $1,471.90