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 $86.70   10.129%   $95.4818   $95.48   $95.50   $95.50  
  Purchase #2 $174.66   9.730%   $191.6544   $191.65   $191.65   $191.70  
  Purchase #3 $235.98   7.116%   $252.7723   $252.77   $252.75   $252.80  
  Purchase #4 $54.65   8.670%   $59.3882   $59.39   $59.40   $59.40  
  Purchase #5 $156.55   5.688%   $165.4546   $165.45   $165.45   $165.50  
  Purchase #6 $84.30   8.735%   $91.6636   $91.66   $91.65   $91.70  
  Purchase #7 $44.48   10.560%   $49.1771   $49.18   $49.20   $49.20  
  7 purchase totals = $837.32       $905.5920   $905.58   $905.60   $905.80