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 $66.55   8.568%   $72.252   $72.25   $72.25   $72.30  
  Purchase #2 $247.65   3.807%   $257.078   $257.08   $257.10   $257.10  
  Purchase #3 $157.37   10.699%   $174.207   $174.21   $174.20   $174.20  
  Purchase #4 $90.82   6.199%   $96.4499   $96.45   $96.45   $96.40  
  Purchase #5 $174.65   13.440%   $198.123   $198.12   $198.10   $198.10  
  Purchase #6 $66.86   12.602%   $75.2857   $75.29   $75.30   $75.30  
  Purchase #7 $208.30   12.455%   $234.2438   $234.24   $234.25   $234.20  
  7 purchase totals = $1,012.20       $1,107.6394   $1,107.64   $1,107.65   $1,107.60