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 $193.76   4.593%   $202.6594   $202.66   $202.65   $202.70  
  Purchase #2 $210.62   3.347%   $217.6695   $217.67   $217.65   $217.70  
  Purchase #3 $121.44   4.776%   $127.24   $127.24   $127.25   $127.20  
  Purchase #4 $49.66   11.128%   $55.1862   $55.19   $55.20   $55.20  
  Purchase #5 $64.76   5.587%   $68.3781   $68.38   $68.40   $68.40  
  Purchase #6 $241.53   8.702%   $262.5479   $262.55   $262.55   $262.50  
  Purchase #7 $200.85   3.609%   $208.0987   $208.10   $208.10   $208.10  
  7 purchase totals = $1,082.62       $1,141.7798   $1,141.79   $1,141.80   $1,141.80