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 $92.33   3.343%   $95.4166   $95.42   $95.40   $95.40  
  Purchase #2 $220.92   6.691%   $235.7018   $235.70   $235.70   $235.70  
  Purchase #3 $181.94   13.593%   $206.6711   $206.67   $206.65   $206.70  
  Purchase #4 $152.54   7.157%   $163.4573   $163.46   $163.45   $163.50  
  Purchase #5 $24.78   8.739%   $26.9455   $26.95   $26.95   $26.90  
  Purchase #6 $250.46   9.679%   $274.702   $274.70   $274.70   $274.70  
  Purchase #7 $238.26   8.798%   $259.2221   $259.22   $259.20   $259.20  
  7 purchase totals = $1,161.23       $1,262.1164   $1,262.12   $1,262.05   $1,262.10