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 $87.77   8.291%   $95.047   $95.05   $95.05   $95.00  
  Purchase #2 $202.83   7.140%   $217.3121   $217.31   $217.30   $217.30  
  Purchase #3 $92.50   13.217%   $104.7257   $104.73   $104.75   $104.70  
  Purchase #4 $222.41   12.448%   $250.0956   $250.10   $250.10   $250.10  
  Purchase #5 $172.77   3.312%   $178.4921   $178.49   $178.50   $178.50  
  Purchase #6 $17.60   6.116%   $18.6764   $18.68   $18.70   $18.70  
  Purchase #7 $156.42   6.664%   $166.8438   $166.84   $166.85   $166.80  
  7 purchase totals = $952.30       $1,031.1927   $1,031.20   $1,031.25   $1,031.10