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 $92.54   3.371%   $95.6595   $95.66   $95.65   $95.70  
  Purchase #2 $145.31   6.276%   $154.4297   $154.43   $154.45   $154.40  
  Purchase #3 $156.74   8.221%   $169.6256   $169.63   $169.65   $169.60  
  Purchase #4 $186.97   11.316%   $208.1275   $208.13   $208.15   $208.10  
  Purchase #5 $235.36   11.670%   $262.8265   $262.83   $262.85   $262.80  
  Purchase #6 $17.52   4.328%   $18.2783   $18.28   $18.30   $18.30  
  Purchase #7 $47.80   3.356%   $49.4042   $49.40   $49.40   $49.40  
  7 purchase totals = $882.24       $958.3513   $958.36   $958.45   $958.30