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 $84.57   10.315%   $93.2934   $93.29   $93.30   $93.30  
  Purchase #2 $214.82   8.275%   $232.5964   $232.60   $232.60   $232.60  
  Purchase #3 $171.93   8.537%   $186.6077   $186.61   $186.60   $186.60  
  Purchase #4 $182.82   5.726%   $193.2883   $193.29   $193.30   $193.30  
  Purchase #5 $176.96   13.798%   $201.3769   $201.38   $201.40   $201.40  
  Purchase #6 $40.42   12.416%   $45.4385   $45.44   $45.45   $45.40  
  Purchase #7 $205.81   8.779%   $223.8781   $223.88   $223.90   $223.90  
  7 purchase totals = $1,077.33       $1,176.4793   $1,176.49   $1,176.55   $1,176.50