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 $208.85   8.330%   $226.2472   $226.25   $226.25   $226.20  
  Purchase #2 $180.76   11.582%   $201.6956   $201.70   $201.70   $201.70  
  Purchase #3 $88.79   13.814%   $101.0555   $101.06   $101.05   $101.10  
  Purchase #4 $79.30   12.413%   $89.1435   $89.14   $89.15   $89.10  
  Purchase #5 $52.31   6.538%   $55.73   $55.73   $55.75   $55.70  
  Purchase #6 $146.74   3.532%   $151.9229   $151.92   $151.90   $151.90  
  Purchase #7 $207.34   10.627%   $229.374   $229.37   $229.35   $229.40  
  7 purchase totals = $964.09       $1,055.1687   $1,055.17   $1,055.15   $1,055.10