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 $86.66   9.664%   $95.0348   $95.03   $95.05   $95.00  
  Purchase #2 $104.76   13.179%   $118.5663   $118.57   $118.55   $118.60  
  Purchase #3 $41.41   12.531%   $46.5991   $46.60   $46.60   $46.60  
  Purchase #4 $190.90   9.501%   $209.0374   $209.04   $209.05   $209.00  
  Purchase #5 $237.96   11.258%   $264.7495   $264.75   $264.75   $264.70  
  Purchase #6 $98.81   5.822%   $104.5627   $104.56   $104.55   $104.60  
  Purchase #7 $206.99   5.343%   $218.0495   $218.05   $218.05   $218.00  
  7 purchase totals = $967.49       $1,056.5993   $1,056.60   $1,056.60   $1,056.50