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 $146.83   10.757%   $162.6245   $162.62   $162.60   $162.60  
  Purchase #2 $158.50   4.227%   $165.1998   $165.20   $165.20   $165.20  
  Purchase #3 $157.78   11.276%   $175.5713   $175.57   $175.55   $175.60  
  Purchase #4 $207.72   4.140%   $216.3196   $216.32   $216.30   $216.30  
  Purchase #5 $158.55   13.846%   $180.5028   $180.50   $180.50   $180.50  
  Purchase #6 $205.71   10.226%   $226.7459   $226.75   $226.75   $226.70  
  Purchase #7 $212.73   11.576%   $237.3556   $237.36   $237.35   $237.40  
  7 purchase totals = $1,247.82       $1,364.3195   $1,364.32   $1,364.25   $1,364.30