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 $236.41   4.605%   $247.2967   $247.30   $247.30   $247.30  
  Purchase #2 $127.38   5.687%   $134.6241   $134.62   $134.60   $134.60  
  Purchase #3 $50.91   11.308%   $56.6669   $56.67   $56.65   $56.70  
  Purchase #4 $244.45   4.532%   $255.5285   $255.53   $255.55   $255.50  
  Purchase #5 $152.59   4.826%   $159.954   $159.95   $159.95   $160.00  
  Purchase #6 $8.48   11.606%   $9.4642   $9.46   $9.45   $9.50  
  Purchase #7 $247.66   3.795%   $257.0587   $257.06   $257.05   $257.10  
  7 purchase totals = $1,067.88       $1,120.5931   $1,120.59   $1,120.55   $1,120.70