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 $59.68   7.116%   $63.9268   $63.93   $63.95   $63.90  
  Purchase #2 $123.88   13.501%   $140.605   $140.61   $140.60   $140.60  
  Purchase #3 $232.87   10.697%   $257.7801   $257.78   $257.80   $257.80  
  Purchase #4 $212.82   13.443%   $241.4294   $241.43   $241.45   $241.40  
  Purchase #5 $120.65   6.577%   $128.5852   $128.59   $128.60   $128.60  
  Purchase #6 $15.41   11.577%   $17.194   $17.19   $17.20   $17.20  
  Purchase #7 $153.31   7.370%   $164.6089   $164.61   $164.60   $164.60  
  7 purchase totals = $918.62       $1,014.1294   $1,014.14   $1,014.20   $1,014.10