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 $42.76   4.682%   $44.762   $44.76   $44.75   $44.80  
  Purchase #2 $170.93   13.318%   $193.6945   $193.69   $193.70   $193.70  
  Purchase #3 $31.31   6.185%   $33.2465   $33.25   $33.25   $33.20  
  Purchase #4 $98.52   7.685%   $106.0913   $106.09   $106.10   $106.10  
  Purchase #5 $167.56   13.540%   $190.2476   $190.25   $190.25   $190.20  
  Purchase #6 $102.73   7.237%   $110.1646   $110.16   $110.15   $110.20  
  Purchase #7 $153.32   5.357%   $161.5334   $161.53   $161.55   $161.50  
  7 purchase totals = $767.13       $839.7399   $839.73   $839.75   $839.70