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 $58.87   4.747%   $61.6646   $61.66   $61.65   $61.70  
  Purchase #2 $186.48   5.428%   $196.6021   $196.60   $196.60   $196.60  
  Purchase #3 $238.61   3.208%   $246.2646   $246.26   $246.25   $246.30  
  Purchase #4 $81.75   3.467%   $84.5843   $84.58   $84.60   $84.60  
  Purchase #5 $250.32   3.111%   $258.1075   $258.11   $258.10   $258.10  
  Purchase #6 $248.97   3.501%   $257.6864   $257.69   $257.70   $257.70  
  Purchase #7 $189.48   11.193%   $210.6885   $210.69   $210.70   $210.70  
  7 purchase totals = $1,254.48       $1,315.5980   $1,315.59   $1,315.60   $1,315.70