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 $197.27   7.772%   $212.6018   $212.60   $212.60   $212.60  
  Purchase #2 $157.30   10.108%   $173.1999   $173.20   $173.20   $173.20  
  Purchase #3 $190.37   11.225%   $211.739   $211.74   $211.75   $211.70  
  Purchase #4 $104.70   3.410%   $108.2703   $108.27   $108.25   $108.30  
  Purchase #5 $190.91   6.828%   $203.9453   $203.95   $203.95   $203.90  
  Purchase #6 $123.38   12.871%   $139.2602   $139.26   $139.25   $139.30  
  Purchase #7 $199.63   3.668%   $206.9524   $206.95   $206.95   $207.00  
  7 purchase totals = $1,163.56       $1,255.9689   $1,255.97   $1,255.95   $1,256.00