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 $182.86   8.732%   $198.8273   $198.83   $198.85   $198.80  
  Purchase #2 $200.62   3.280%   $207.2003   $207.20   $207.20   $207.20  
  Purchase #3 $114.26   10.663%   $126.4435   $126.44   $126.45   $126.40  
  Purchase #4 $69.48   6.699%   $74.1345   $74.13   $74.15   $74.10  
  Purchase #5 $205.32   13.830%   $233.7158   $233.72   $233.70   $233.70  
  Purchase #6 $232.82   3.567%   $241.1247   $241.12   $241.10   $241.10  
  Purchase #7 $162.72   5.686%   $171.9723   $171.97   $171.95   $172.00  
  7 purchase totals = $1,168.08       $1,253.4184   $1,253.41   $1,253.40   $1,253.30