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 $61.34   5.836%   $64.9198   $64.92   $64.90   $64.90  
  Purchase #2 $26.54   13.801%   $30.2028   $30.20   $30.20   $30.20  
  Purchase #3 $177.78   4.731%   $186.1908   $186.19   $186.20   $186.20  
  Purchase #4 $207.75   9.144%   $226.7467   $226.75   $226.75   $226.70  
  Purchase #5 $232.99   10.847%   $258.2624   $258.26   $258.25   $258.30  
  Purchase #6 $39.73   11.835%   $44.432   $44.43   $44.45   $44.40  
  Purchase #7 $143.89   5.745%   $152.1565   $152.16   $152.15   $152.20  
  7 purchase totals = $890.02       $962.9110   $962.91   $962.90   $962.90