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 $69.44   5.214%   $73.0606   $73.06   $73.05   $73.10  
  Purchase #2 $198.36   11.512%   $221.1952   $221.20   $221.20   $221.20  
  Purchase #3 $53.32   11.469%   $59.4353   $59.44   $59.45   $59.40  
  Purchase #4 $211.25   7.787%   $227.7   $227.70   $227.70   $227.70  
  Purchase #5 $19.25   10.237%   $21.2206   $21.22   $21.20   $21.20  
  Purchase #6 $241.58   6.847%   $258.121   $258.12   $258.10   $258.10  
  Purchase #7 $33.72   11.192%   $37.4939   $37.49   $37.50   $37.50  
  7 purchase totals = $826.92       $898.2266   $898.23   $898.20   $898.20