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 $62.86   7.488%   $67.567   $67.57   $67.55   $67.60  
  Purchase #2 $148.37   10.459%   $163.888   $163.89   $163.90   $163.90  
  Purchase #3 $95.34   5.312%   $100.4045   $100.40   $100.40   $100.40  
  Purchase #4 $146.57   11.312%   $163.15   $163.15   $163.15   $163.20  
  Purchase #5 $159.60   3.293%   $164.8556   $164.86   $164.85   $164.90  
  Purchase #6 $203.62   8.456%   $220.8381   $220.84   $220.85   $220.80  
  Purchase #7 $14.78   11.516%   $16.4821   $16.48   $16.50   $16.50  
  7 purchase totals = $831.14       $897.1853   $897.19   $897.20   $897.30