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 $151.27   8.864%   $164.6786   $164.68   $164.70   $164.70  
  Purchase #2 $245.80   9.540%   $269.2493   $269.25   $269.25   $269.20  
  Purchase #3 $173.49   5.196%   $182.5045   $182.50   $182.50   $182.50  
  Purchase #4 $147.71   6.695%   $157.5992   $157.60   $157.60   $157.60  
  Purchase #5 $114.45   8.429%   $124.097   $124.10   $124.10   $124.10  
  Purchase #6 $132.43   11.837%   $148.1057   $148.11   $148.10   $148.10  
  Purchase #7 $144.26   3.828%   $149.7823   $149.78   $149.80   $149.80  
  7 purchase totals = $1,109.41       $1,196.0166   $1,196.02   $1,196.05   $1,196.00