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 $177.59   13.570%   $201.689   $201.69   $201.70   $201.70  
  Purchase #2 $119.33   9.478%   $130.6401   $130.64   $130.65   $130.60  
  Purchase #3 $141.41   7.532%   $152.061   $152.06   $152.05   $152.10  
  Purchase #4 $101.77   5.724%   $107.5953   $107.60   $107.60   $107.60  
  Purchase #5 $130.51   5.519%   $137.7128   $137.71   $137.70   $137.70  
  Purchase #6 $125.99   4.568%   $131.7452   $131.75   $131.75   $131.70  
  Purchase #7 $182.62   8.650%   $198.4166   $198.42   $198.40   $198.40  
  7 purchase totals = $979.22       $1,059.8600   $1,059.87   $1,059.85   $1,059.80