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 $207.51   11.656%   $231.6974   $231.70   $231.70   $231.70  
  Purchase #2 $236.82   7.548%   $254.6952   $254.70   $254.70   $254.70  
  Purchase #3 $216.87   5.186%   $228.1169   $228.12   $228.10   $228.10  
  Purchase #4 $59.39   8.843%   $64.6419   $64.64   $64.65   $64.60  
  Purchase #5 $113.77   8.429%   $123.3597   $123.36   $123.35   $123.40  
  Purchase #6 $174.71   5.133%   $183.6779   $183.68   $183.70   $183.70  
  Purchase #7 $18.99   9.217%   $20.7403   $20.74   $20.75   $20.70  
  7 purchase totals = $1,028.06       $1,106.9293   $1,106.94   $1,106.95   $1,106.90