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 $22.95   13.553%   $26.0604   $26.06   $26.05   $26.10  
  Purchase #2 $213.32   9.285%   $233.1268   $233.13   $233.15   $233.10  
  Purchase #3 $125.31   13.313%   $141.9925   $141.99   $142.00   $142.00  
  Purchase #4 $152.28   12.643%   $171.5328   $171.53   $171.55   $171.50  
  Purchase #5 $202.42   6.686%   $215.9538   $215.95   $215.95   $216.00  
  Purchase #6 $13.30   12.236%   $14.9274   $14.93   $14.95   $14.90  
  Purchase #7 $121.51   5.671%   $128.4008   $128.40   $128.40   $128.40  
  7 purchase totals = $851.09       $931.9945   $931.99   $932.05   $932.00