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 $94.41   3.469%   $97.6851   $97.69   $97.70   $97.70  
  Purchase #2 $150.42   11.255%   $167.3498   $167.35   $167.35   $167.30  
  Purchase #3 $92.61   9.703%   $101.5959   $101.60   $101.60   $101.60  
  Purchase #4 $108.80   11.868%   $121.7124   $121.71   $121.70   $121.70  
  Purchase #5 $113.42   12.190%   $127.2459   $127.25   $127.25   $127.20  
  Purchase #6 $112.81   6.813%   $120.4957   $120.50   $120.50   $120.50  
  Purchase #7 $26.34   4.333%   $27.4813   $27.48   $27.50   $27.50  
  7 purchase totals = $698.81       $763.5661   $763.58   $763.60   $763.50