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 $87.78   8.372%   $95.1289   $95.13   $95.15   $95.10  
  Purchase #2 $232.54   10.835%   $257.7357   $257.74   $257.75   $257.70  
  Purchase #3 $25.68   5.670%   $27.1361   $27.14   $27.15   $27.10  
  Purchase #4 $249.57   3.835%   $259.141   $259.14   $259.15   $259.10  
  Purchase #5 $212.82   3.534%   $220.3411   $220.34   $220.35   $220.30  
  Purchase #6 $221.57   12.110%   $248.4021   $248.40   $248.40   $248.40  
  Purchase #7 $232.70   10.550%   $257.2499   $257.25   $257.25   $257.20  
  7 purchase totals = $1,262.66       $1,365.1348   $1,365.14   $1,365.20   $1,364.90