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 $49.71   5.164%   $52.277   $52.28   $52.30   $52.30  
  Purchase #2 $191.65   9.721%   $210.2803   $210.28   $210.30   $210.30  
  Purchase #3 $193.27   6.615%   $206.0548   $206.05   $206.05   $206.10  
  Purchase #4 $216.26   8.520%   $234.6854   $234.69   $234.70   $234.70  
  Purchase #5 $95.70   6.795%   $102.2028   $102.20   $102.20   $102.20  
  Purchase #6 $163.69   4.725%   $171.4244   $171.42   $171.40   $171.40  
  Purchase #7 $144.69   9.345%   $158.2113   $158.21   $158.20   $158.20  
  7 purchase totals = $1,054.97       $1,135.1360   $1,135.13   $1,135.15   $1,135.20