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 $183.47   6.869%   $196.0726   $196.07   $196.05   $196.10  
  Purchase #2 $161.70   8.422%   $175.3184   $175.32   $175.30   $175.30  
  Purchase #3 $44.28   7.749%   $47.7113   $47.71   $47.70   $47.70  
  Purchase #4 $22.46   13.790%   $25.5572   $25.56   $25.55   $25.60  
  Purchase #5 $208.89   10.864%   $231.5838   $231.58   $231.60   $231.60  
  Purchase #6 $230.38   4.408%   $240.5352   $240.54   $240.55   $240.50  
  Purchase #7 $8.93   6.744%   $9.5322   $9.53   $9.55   $9.50  
  7 purchase totals = $860.11       $926.3107   $926.31   $926.30   $926.30