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 $203.95   5.569%   $215.308   $215.31   $215.30   $215.30  
  Purchase #2 $114.32   6.531%   $121.7862   $121.79   $121.80   $121.80  
  Purchase #3 $244.56   9.686%   $268.2481   $268.25   $268.25   $268.20  
  Purchase #4 $53.75   7.348%   $57.6996   $57.70   $57.70   $57.70  
  Purchase #5 $165.33   6.755%   $176.498   $176.50   $176.50   $176.50  
  Purchase #6 $198.74   5.790%   $210.247   $210.25   $210.25   $210.20  
  Purchase #7 $42.87   12.131%   $48.0706   $48.07   $48.05   $48.10  
  7 purchase totals = $1,023.52       $1,097.8575   $1,097.87   $1,097.85   $1,097.80