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 $206.87   8.587%   $224.6339   $224.63   $224.65   $224.60  
  Purchase #2 $32.65   3.818%   $33.8966   $33.90   $33.90   $33.90  
  Purchase #3 $67.27   6.718%   $71.7892   $71.79   $71.80   $71.80  
  Purchase #4 $134.97   9.709%   $148.0742   $148.07   $148.05   $148.10  
  Purchase #5 $83.59   3.205%   $86.2691   $86.27   $86.25   $86.30  
  Purchase #6 $233.97   8.308%   $253.4082   $253.41   $253.40   $253.40  
  Purchase #7 $53.62   6.197%   $56.9428   $56.94   $56.95   $56.90  
  7 purchase totals = $812.94       $875.0140   $875.01   $875.00   $875.00