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 $11.27   3.398%   $11.653   $11.65   $11.65   $11.70  
  Purchase #2 $200.81   13.374%   $227.6663   $227.67   $227.65   $227.70  
  Purchase #3 $156.64   4.617%   $163.8721   $163.87   $163.85   $163.90  
  Purchase #4 $221.65   5.248%   $233.2822   $233.28   $233.30   $233.30  
  Purchase #5 $162.73   13.405%   $184.544   $184.54   $184.55   $184.50  
  Purchase #6 $64.66   5.204%   $68.0249   $68.02   $68.00   $68.00  
  Purchase #7 $56.71   9.607%   $62.1581   $62.16   $62.15   $62.20  
  7 purchase totals = $874.47       $951.2006   $951.19   $951.15   $951.30