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 $23.96   9.212%   $26.1672   $26.17   $26.15   $26.20  
  Purchase #2 $74.72   10.686%   $82.7046   $82.70   $82.70   $82.70  
  Purchase #3 $245.37   4.207%   $255.6927   $255.69   $255.70   $255.70  
  Purchase #4 $96.46   3.647%   $99.9779   $99.98   $100.00   $100.00  
  Purchase #5 $154.48   6.442%   $164.4316   $164.43   $164.45   $164.40  
  Purchase #6 $193.87   10.787%   $214.7828   $214.78   $214.80   $214.80  
  Purchase #7 $176.86   3.291%   $182.6805   $182.68   $182.70   $182.70  
  7 purchase totals = $965.72       $1,026.4373   $1,026.43   $1,026.50   $1,026.50