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 $88.51   7.448%   $95.1022   $95.10   $95.10   $95.10  
  Purchase #2 $232.27   3.823%   $241.1497   $241.15   $241.15   $241.10  
  Purchase #3 $233.99   13.706%   $266.0607   $266.06   $266.05   $266.10  
  Purchase #4 $173.63   8.410%   $188.2323   $188.23   $188.25   $188.20  
  Purchase #5 $214.79   8.697%   $233.4703   $233.47   $233.45   $233.50  
  Purchase #6 $130.93   12.144%   $146.8301   $146.83   $146.85   $146.80  
  Purchase #7 $204.69   12.632%   $230.5464   $230.55   $230.55   $230.50  
  7 purchase totals = $1,278.81       $1,401.3917   $1,401.39   $1,401.40   $1,401.30