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 $237.84   10.177%   $262.045   $262.05   $262.05   $262.00  
  Purchase #2 $71.92   6.113%   $76.3165   $76.32   $76.30   $76.30  
  Purchase #3 $63.34   12.322%   $71.1448   $71.14   $71.15   $71.10  
  Purchase #4 $206.45   3.137%   $212.9263   $212.93   $212.95   $212.90  
  Purchase #5 $92.79   8.798%   $100.9537   $100.95   $100.95   $101.00  
  Purchase #6 $220.95   11.349%   $246.0256   $246.03   $246.05   $246.00  
  Purchase #7 $125.89   11.716%   $140.6393   $140.64   $140.65   $140.60  
  7 purchase totals = $1,019.18       $1,110.0512   $1,110.06   $1,110.10   $1,109.90