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 $184.37   5.843%   $195.1427   $195.14   $195.15   $195.10  
  Purchase #2 $201.83   4.706%   $211.3281   $211.33   $211.35   $211.30  
  Purchase #3 $186.82   10.865%   $207.118   $207.12   $207.10   $207.10  
  Purchase #4 $250.88   5.799%   $265.4285   $265.43   $265.45   $265.40  
  Purchase #5 $44.57   3.769%   $46.2498   $46.25   $46.25   $46.20  
  Purchase #6 $89.58   12.670%   $100.9298   $100.93   $100.95   $100.90  
  Purchase #7 $86.87   11.158%   $96.563   $96.56   $96.55   $96.60  
  7 purchase totals = $1,044.92       $1,122.7599   $1,122.76   $1,122.80   $1,122.60