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 $11.67   10.811%   $12.9316   $12.93   $12.95   $12.90  
  Purchase #2 $86.54   10.599%   $95.7124   $95.71   $95.70   $95.70  
  Purchase #3 $45.51   4.373%   $47.5002   $47.50   $47.50   $47.50  
  Purchase #4 $248.30   4.222%   $258.7832   $258.78   $258.80   $258.80  
  Purchase #5 $163.95   9.397%   $179.3564   $179.36   $179.35   $179.40  
  Purchase #6 $182.52   13.280%   $206.7587   $206.76   $206.75   $206.80  
  Purchase #7 $244.83   3.702%   $253.8936   $253.89   $253.90   $253.90  
  7 purchase totals = $983.32       $1,054.9361   $1,054.93   $1,054.95   $1,055.00