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 $194.89   5.470%   $205.5505   $205.55   $205.55   $205.60  
  Purchase #2 $97.26   13.742%   $110.6255   $110.63   $110.65   $110.60  
  Purchase #3 $50.26   7.771%   $54.1657   $54.17   $54.15   $54.20  
  Purchase #4 $114.66   12.148%   $128.5889   $128.59   $128.60   $128.60  
  Purchase #5 $155.88   3.601%   $161.4932   $161.49   $161.50   $161.50  
  Purchase #6 $199.67   4.811%   $209.2761   $209.28   $209.30   $209.30  
  Purchase #7 $214.93   8.611%   $233.4376   $233.44   $233.45   $233.40  
  7 purchase totals = $1,027.55       $1,103.1375   $1,103.15   $1,103.20   $1,103.20