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 $43.73   9.652%   $47.9508   $47.95   $47.95   $48.00  
  Purchase #2 $204.35   3.607%   $211.7209   $211.72   $211.70   $211.70  
  Purchase #3 $177.92   13.744%   $202.3733   $202.37   $202.35   $202.40  
  Purchase #4 $217.78   8.312%   $235.8819   $235.88   $235.90   $235.90  
  Purchase #5 $114.93   8.483%   $124.6795   $124.68   $124.70   $124.70  
  Purchase #6 $198.30   3.680%   $205.5974   $205.60   $205.60   $205.60  
  Purchase #7 $226.30   3.527%   $234.2816   $234.28   $234.30   $234.30  
  7 purchase totals = $1,183.31       $1,262.4854   $1,262.48   $1,262.50   $1,262.60