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 $64.89   6.364%   $69.0196   $69.02   $69.00   $69.00  
  Purchase #2 $226.42   4.531%   $236.6791   $236.68   $236.70   $236.70  
  Purchase #3 $86.49   10.342%   $95.4348   $95.43   $95.45   $95.40  
  Purchase #4 $121.55   4.382%   $126.8763   $126.88   $126.90   $126.90  
  Purchase #5 $213.56   6.724%   $227.9198   $227.92   $227.90   $227.90  
  Purchase #6 $165.29   5.739%   $174.776   $174.78   $174.80   $174.80  
  Purchase #7 $148.57   12.440%   $167.0521   $167.05   $167.05   $167.10  
  7 purchase totals = $1,026.77       $1,097.7577   $1,097.76   $1,097.80   $1,097.80