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 $195.86   9.636%   $214.7331   $214.73   $214.75   $214.70  
  Purchase #2 $236.68   11.147%   $263.0627   $263.06   $263.05   $263.10  
  Purchase #3 $102.26   9.398%   $111.8704   $111.87   $111.85   $111.90  
  Purchase #4 $183.85   13.349%   $208.3921   $208.39   $208.40   $208.40  
  Purchase #5 $213.54   11.760%   $238.6523   $238.65   $238.65   $238.70  
  Purchase #6 $55.73   7.256%   $59.7738   $59.77   $59.75   $59.80  
  Purchase #7 $127.87   9.645%   $140.2031   $140.20   $140.20   $140.20  
  7 purchase totals = $1,115.79       $1,236.6875   $1,236.67   $1,236.65   $1,236.80