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 $174.49   12.172%   $195.7289   $195.73   $195.75   $195.70  
  Purchase #2 $185.91   13.825%   $211.6121   $211.61   $211.60   $211.60  
  Purchase #3 $31.74   11.787%   $35.4812   $35.48   $35.50   $35.50  
  Purchase #4 $237.77   5.354%   $250.5002   $250.50   $250.50   $250.50  
  Purchase #5 $189.64   8.851%   $206.425   $206.43   $206.45   $206.40  
  Purchase #6 $27.67   13.124%   $31.3014   $31.30   $31.30   $31.30  
  Purchase #7 $23.39   3.263%   $24.1532   $24.15   $24.15   $24.20  
  7 purchase totals = $870.61       $955.2020   $955.20   $955.25   $955.20