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 $61.95   12.347%   $69.599   $69.60   $69.60   $69.60  
  Purchase #2 $147.55   6.489%   $157.1245   $157.12   $157.10   $157.10  
  Purchase #3 $24.46   4.505%   $25.5619   $25.56   $25.55   $25.60  
  Purchase #4 $211.79   6.744%   $226.0731   $226.07   $226.05   $226.10  
  Purchase #5 $199.39   3.546%   $206.4604   $206.46   $206.45   $206.50  
  Purchase #6 $10.47   13.709%   $11.9053   $11.91   $11.90   $11.90  
  Purchase #7 $140.48   10.214%   $154.8286   $154.83   $154.85   $154.80  
  7 purchase totals = $796.09       $851.5528   $851.55   $851.50   $851.60