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 $205.28   5.544%   $216.6607   $216.66   $216.65   $216.70  
  Purchase #2 $241.87   7.330%   $259.5991   $259.60   $259.60   $259.60  
  Purchase #3 $26.50   6.791%   $28.2996   $28.30   $28.30   $28.30  
  Purchase #4 $117.99   6.609%   $125.788   $125.79   $125.80   $125.80  
  Purchase #5 $211.34   5.158%   $222.2409   $222.24   $222.25   $222.20  
  Purchase #6 $208.49   7.245%   $223.5951   $223.60   $223.60   $223.60  
  Purchase #7 $39.58   12.686%   $44.6011   $44.60   $44.60   $44.60  
  7 purchase totals = $1,051.05       $1,120.7845   $1,120.79   $1,120.80   $1,120.80