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 $127.76   11.459%   $142.4   $142.40   $142.40   $142.40  
  Purchase #2 $95.42   11.135%   $106.045   $106.05   $106.05   $106.00  
  Purchase #3 $78.28   8.148%   $84.6583   $84.66   $84.65   $84.70  
  Purchase #4 $72.51   8.727%   $78.8379   $78.84   $78.85   $78.80  
  Purchase #5 $59.73   5.576%   $63.0605   $63.06   $63.05   $63.10  
  Purchase #6 $243.47   9.831%   $267.4055   $267.41   $267.40   $267.40  
  Purchase #7 $13.84   12.760%   $15.606   $15.61   $15.60   $15.60  
  7 purchase totals = $691.01       $758.0132   $758.03   $758.00   $758.00