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 $60.62   10.546%   $67.013   $67.01   $67.00   $67.00  
  Purchase #2 $90.82   13.194%   $102.8028   $102.80   $102.80   $102.80  
  Purchase #3 $17.54   6.379%   $18.6589   $18.66   $18.65   $18.70  
  Purchase #4 $153.71   7.751%   $165.6241   $165.62   $165.60   $165.60  
  Purchase #5 $206.32   7.797%   $222.4068   $222.41   $222.40   $222.40  
  Purchase #6 $179.33   12.366%   $201.5059   $201.51   $201.50   $201.50  
  Purchase #7 $171.41   9.667%   $187.9802   $187.98   $188.00   $188.00  
  7 purchase totals = $879.75       $965.9917   $965.99   $965.95   $966.00