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 $92.51   5.848%   $97.92   $97.92   $97.90   $97.90  
  Purchase #2 $94.63   4.427%   $98.8193   $98.82   $98.80   $98.80  
  Purchase #3 $192.68   13.405%   $218.5088   $218.51   $218.50   $218.50  
  Purchase #4 $175.38   12.724%   $197.6954   $197.70   $197.70   $197.70  
  Purchase #5 $141.83   5.398%   $149.486   $149.49   $149.50   $149.50  
  Purchase #6 $208.38   6.582%   $222.0956   $222.10   $222.10   $222.10  
  Purchase #7 $88.51   4.282%   $92.3   $92.30   $92.30   $92.30  
  7 purchase totals = $993.92       $1,076.8251   $1,076.84   $1,076.80   $1,076.80