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 $194.27   7.552%   $208.9413   $208.94   $208.95   $208.90  
  Purchase #2 $138.48   10.252%   $152.677   $152.68   $152.70   $152.70  
  Purchase #3 $95.83   5.756%   $101.346   $101.35   $101.35   $101.30  
  Purchase #4 $211.90   8.661%   $230.2527   $230.25   $230.25   $230.30  
  Purchase #5 $192.31   10.280%   $212.0795   $212.08   $212.10   $212.10  
  Purchase #6 $11.67   12.665%   $13.148   $13.15   $13.15   $13.10  
  Purchase #7 $218.28   13.863%   $248.5402   $248.54   $248.55   $248.50  
  7 purchase totals = $1,062.74       $1,166.9847   $1,166.99   $1,167.05   $1,166.90