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 $59.34   4.541%   $62.0346   $62.03   $62.05   $62.00  
  Purchase #2 $193.80   12.683%   $218.3797   $218.38   $218.40   $218.40  
  Purchase #3 $16.91   10.466%   $18.6798   $18.68   $18.70   $18.70  
  Purchase #4 $191.30   5.355%   $201.5441   $201.54   $201.55   $201.50  
  Purchase #5 $58.76   8.501%   $63.7552   $63.76   $63.75   $63.80  
  Purchase #6 $166.63   8.742%   $181.1968   $181.20   $181.20   $181.20  
  Purchase #7 $21.48   12.609%   $24.1884   $24.19   $24.20   $24.20  
  7 purchase totals = $708.22       $769.7786   $769.78   $769.85   $769.80