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 $241.67   8.226%   $261.5498   $261.55   $261.55   $261.50  
  Purchase #2 $198.47   13.519%   $225.3012   $225.30   $225.30   $225.30  
  Purchase #3 $65.40   5.293%   $68.8616   $68.86   $68.85   $68.90  
  Purchase #4 $77.76   7.709%   $83.7545   $83.75   $83.75   $83.80  
  Purchase #5 $152.54   12.431%   $171.5022   $171.50   $171.50   $171.50  
  Purchase #6 $131.62   8.640%   $142.992   $142.99   $143.00   $143.00  
  Purchase #7 $150.47   7.805%   $162.2142   $162.21   $162.20   $162.20  
  7 purchase totals = $1,017.93       $1,116.1755   $1,116.16   $1,116.15   $1,116.20