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 $89.60   6.753%   $95.6507   $95.65   $95.65   $95.70  
  Purchase #2 $188.70   12.606%   $212.4875   $212.49   $212.50   $212.50  
  Purchase #3 $60.62   3.469%   $62.7229   $62.72   $62.70   $62.70  
  Purchase #4 $212.77   11.676%   $237.613   $237.61   $237.60   $237.60  
  Purchase #5 $62.72   5.329%   $66.0623   $66.06   $66.05   $66.10  
  Purchase #6 $192.69   12.589%   $216.9477   $216.95   $216.95   $216.90  
  Purchase #7 $200.53   3.802%   $208.1542   $208.15   $208.15   $208.20  
  7 purchase totals = $1,007.63       $1,099.6383   $1,099.63   $1,099.60   $1,099.70