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 $48.82   7.593%   $52.5269   $52.53   $52.55   $52.50  
  Purchase #2 $230.58   6.553%   $245.6899   $245.69   $245.70   $245.70  
  Purchase #3 $234.66   3.489%   $242.8473   $242.85   $242.85   $242.80  
  Purchase #4 $121.86   10.402%   $134.5359   $134.54   $134.55   $134.50  
  Purchase #5 $95.77   5.621%   $101.1532   $101.15   $101.15   $101.20  
  Purchase #6 $200.77   11.711%   $224.2822   $224.28   $224.30   $224.30  
  Purchase #7 $112.48   13.547%   $127.7177   $127.72   $127.70   $127.70  
  7 purchase totals = $1,044.94       $1,128.7531   $1,128.76   $1,128.80   $1,128.70