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 $43.41   11.871%   $48.5632   $48.56   $48.55   $48.60  
  Purchase #2 $198.60   8.804%   $216.0847   $216.08   $216.10   $216.10  
  Purchase #3 $188.85   12.580%   $212.6073   $212.61   $212.60   $212.60  
  Purchase #4 $36.42   11.724%   $40.6899   $40.69   $40.70   $40.70  
  Purchase #5 $161.93   3.481%   $167.5668   $167.57   $167.55   $167.60  
  Purchase #6 $180.59   7.761%   $194.6056   $194.61   $194.60   $194.60  
  Purchase #7 $23.60   13.618%   $26.8138   $26.81   $26.80   $26.80  
  7 purchase totals = $833.40       $906.9313   $906.93   $906.90   $907.00