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 $62.36   5.524%   $65.8048   $65.80   $65.80   $65.80  
  Purchase #2 $152.93   8.366%   $165.7241   $165.72   $165.70   $165.70  
  Purchase #3 $225.53   13.861%   $256.7907   $256.79   $256.80   $256.80  
  Purchase #4 $144.31   11.723%   $161.2275   $161.23   $161.25   $161.20  
  Purchase #5 $182.61   13.625%   $207.4906   $207.49   $207.50   $207.50  
  Purchase #6 $230.69   9.847%   $253.406   $253.41   $253.40   $253.40  
  Purchase #7 $111.33   12.403%   $125.1383   $125.14   $125.15   $125.10  
  7 purchase totals = $1,109.76       $1,235.5820   $1,235.58   $1,235.60   $1,235.50