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 $84.30   10.433%   $93.095   $93.10   $93.10   $93.10  
  Purchase #2 $207.41   3.359%   $214.3769   $214.38   $214.40   $214.40  
  Purchase #3 $200.96   3.490%   $207.9735   $207.97   $207.95   $208.00  
  Purchase #4 $225.48   5.103%   $236.9862   $236.99   $237.00   $237.00  
  Purchase #5 $17.83   5.227%   $18.762   $18.76   $18.75   $18.80  
  Purchase #6 $201.26   5.817%   $212.9673   $212.97   $212.95   $213.00  
  Purchase #7 $81.54   13.849%   $92.8325   $92.83   $92.85   $92.80  
  7 purchase totals = $1,018.78       $1,076.9934   $1,077.00   $1,077.00   $1,077.10