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 $55.76   12.303%   $62.6202   $62.62   $62.60   $62.60  
  Purchase #2 $122.65   8.496%   $133.0703   $133.07   $133.05   $133.10  
  Purchase #3 $22.73   5.302%   $23.9351   $23.94   $23.95   $23.90  
  Purchase #4 $226.60   5.839%   $239.8312   $239.83   $239.85   $239.80  
  Purchase #5 $57.99   9.406%   $63.4445   $63.44   $63.45   $63.40  
  Purchase #6 $26.97   4.342%   $28.141   $28.14   $28.15   $28.10  
  Purchase #7 $184.61   8.742%   $200.7486   $200.75   $200.75   $200.70  
  7 purchase totals = $697.31       $751.7909   $751.79   $751.80   $751.60