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 $87.58   5.501%   $92.3978   $92.40   $92.40   $92.40  
  Purchase #2 $61.45   12.531%   $69.1503   $69.15   $69.15   $69.20  
  Purchase #3 $224.97   4.151%   $234.3085   $234.31   $234.30   $234.30  
  Purchase #4 $135.54   8.397%   $146.9213   $146.92   $146.90   $146.90  
  Purchase #5 $152.99   5.173%   $160.9042   $160.90   $160.90   $160.90  
  Purchase #6 $156.72   4.457%   $163.705   $163.71   $163.70   $163.70  
  Purchase #7 $226.41   3.278%   $233.8317   $233.83   $233.85   $233.80  
  7 purchase totals = $1,045.66       $1,101.2188   $1,101.22   $1,101.20   $1,101.20