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 $23.58   9.248%   $25.7607   $25.76   $25.75   $25.80  
  Purchase #2 $152.78   9.614%   $167.4683   $167.47   $167.45   $167.50  
  Purchase #3 $242.68   3.131%   $250.2783   $250.28   $250.30   $250.30  
  Purchase #4 $183.37   5.447%   $193.3582   $193.36   $193.35   $193.40  
  Purchase #5 $63.97   13.661%   $72.7089   $72.71   $72.70   $72.70  
  Purchase #6 $196.52   9.513%   $215.2149   $215.21   $215.20   $215.20  
  Purchase #7 $195.59   3.416%   $202.2714   $202.27   $202.25   $202.30  
  7 purchase totals = $1,058.49       $1,127.0607   $1,127.06   $1,127.00   $1,127.20