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 $217.77   8.520%   $236.324   $236.32   $236.30   $236.30  
  Purchase #2 $206.42   8.276%   $223.5033   $223.50   $223.50   $223.50  
  Purchase #3 $190.63   4.485%   $199.1798   $199.18   $199.20   $199.20  
  Purchase #4 $82.31   11.115%   $91.4588   $91.46   $91.45   $91.50  
  Purchase #5 $133.69   9.695%   $146.6512   $146.65   $146.65   $146.70  
  Purchase #6 $117.94   13.805%   $134.2216   $134.22   $134.20   $134.20  
  Purchase #7 $143.27   13.347%   $162.3922   $162.39   $162.40   $162.40  
  7 purchase totals = $1,092.03       $1,193.7309   $1,193.72   $1,193.70   $1,193.80