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 $32.60   13.550%   $37.0173   $37.02   $37.00   $37.00  
  Purchase #2 $102.79   4.447%   $107.3611   $107.36   $107.35   $107.40  
  Purchase #3 $187.25   13.867%   $213.216   $213.22   $213.20   $213.20  
  Purchase #4 $249.95   3.615%   $258.9857   $258.99   $259.00   $259.00  
  Purchase #5 $161.94   8.801%   $176.1923   $176.19   $176.20   $176.20  
  Purchase #6 $65.54   9.675%   $71.881   $71.88   $71.90   $71.90  
  Purchase #7 $161.74   9.289%   $176.764   $176.76   $176.75   $176.80  
  7 purchase totals = $961.81       $1,041.4174   $1,041.42   $1,041.40   $1,041.50