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 $105.63   8.657%   $114.7744   $114.77   $114.75   $114.80  
  Purchase #2 $23.77   3.689%   $24.6469   $24.65   $24.65   $24.60  
  Purchase #3 $193.57   11.687%   $216.1925   $216.19   $216.20   $216.20  
  Purchase #4 $191.96   11.853%   $214.713   $214.71   $214.70   $214.70  
  Purchase #5 $170.46   12.312%   $191.447   $191.45   $191.45   $191.40  
  Purchase #6 $247.63   7.708%   $266.7173   $266.72   $266.70   $266.70  
  Purchase #7 $80.71   4.314%   $84.1918   $84.19   $84.20   $84.20  
  7 purchase totals = $1,013.73       $1,112.6829   $1,112.68   $1,112.65   $1,112.60