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 $69.27   10.667%   $76.659   $76.66   $76.65   $76.70  
  Purchase #2 $128.41   12.374%   $144.2995   $144.30   $144.30   $144.30  
  Purchase #3 $74.98   12.225%   $84.1463   $84.15   $84.15   $84.10  
  Purchase #4 $160.57   11.265%   $178.6582   $178.66   $178.65   $178.70  
  Purchase #5 $249.33   13.353%   $282.623   $282.62   $282.60   $282.60  
  Purchase #6 $65.90   3.606%   $68.2764   $68.28   $68.30   $68.30  
  Purchase #7 $118.88   8.691%   $129.2119   $129.21   $129.20   $129.20  
  7 purchase totals = $867.34       $963.8743   $963.88   $963.85   $963.90