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 $131.90   7.468%   $141.7503   $141.75   $141.75   $141.80  
  Purchase #2 $246.93   13.838%   $281.1002   $281.10   $281.10   $281.10  
  Purchase #3 $245.44   6.423%   $261.2046   $261.20   $261.20   $261.20  
  Purchase #4 $239.75   7.609%   $257.9926   $257.99   $258.00   $258.00  
  Purchase #5 $97.44   6.288%   $103.567   $103.57   $103.55   $103.60  
  Purchase #6 $78.51   13.606%   $89.1921   $89.19   $89.20   $89.20  
  Purchase #7 $61.88   4.125%   $64.4326   $64.43   $64.45   $64.40  
  7 purchase totals = $1,101.85       $1,199.2394   $1,199.23   $1,199.25   $1,199.30