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 $24.87   3.662%   $25.7807   $25.78   $25.80   $25.80  
  Purchase #2 $54.75   12.745%   $61.7279   $61.73   $61.75   $61.70  
  Purchase #3 $109.45   4.653%   $114.5427   $114.54   $114.55   $114.50  
  Purchase #4 $210.65   6.316%   $223.9547   $223.95   $223.95   $224.00  
  Purchase #5 $211.60   7.306%   $227.0595   $227.06   $227.05   $227.10  
  Purchase #6 $247.34   3.320%   $255.5517   $255.55   $255.55   $255.60  
  Purchase #7 $98.87   3.483%   $102.3136   $102.31   $102.30   $102.30  
  7 purchase totals = $957.53       $1,010.9308   $1,010.92   $1,010.95   $1,011.00