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 $86.83   7.392%   $93.2485   $93.25   $93.25   $93.20  
  Purchase #2 $62.50   5.844%   $66.1525   $66.15   $66.15   $66.20  
  Purchase #3 $77.89   13.335%   $88.2766   $88.28   $88.30   $88.30  
  Purchase #4 $184.68   12.303%   $207.4012   $207.40   $207.40   $207.40  
  Purchase #5 $225.49   4.474%   $235.5784   $235.58   $235.60   $235.60  
  Purchase #6 $102.78   11.150%   $114.24   $114.24   $114.25   $114.20  
  Purchase #7 $133.80   4.855%   $140.296   $140.30   $140.30   $140.30  
  7 purchase totals = $873.97       $945.1932   $945.20   $945.25   $945.20