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 $241.33   8.160%   $261.0225   $261.02   $261.00   $261.00  
  Purchase #2 $191.29   4.247%   $199.4141   $199.41   $199.40   $199.40  
  Purchase #3 $8.43   7.176%   $9.0349   $9.03   $9.05   $9.00  
  Purchase #4 $158.86   7.860%   $171.3464   $171.35   $171.35   $171.30  
  Purchase #5 $236.74   7.447%   $254.37   $254.37   $254.35   $254.40  
  Purchase #6 $172.97   6.388%   $184.0193   $184.02   $184.00   $184.00  
  Purchase #7 $14.95   11.648%   $16.6914   $16.69   $16.70   $16.70  
  7 purchase totals = $1,024.57       $1,095.8986   $1,095.89   $1,095.85   $1,095.80