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 $232.47   7.518%   $249.9471   $249.95   $249.95   $249.90  
  Purchase #2 $231.37   3.446%   $239.343   $239.34   $239.35   $239.30  
  Purchase #3 $164.43   10.421%   $181.5653   $181.57   $181.55   $181.60  
  Purchase #4 $163.79   8.677%   $178.0021   $178.00   $178.00   $178.00  
  Purchase #5 $75.72   5.206%   $79.662   $79.66   $79.65   $79.70  
  Purchase #6 $56.48   10.847%   $62.6064   $62.61   $62.60   $62.60  
  Purchase #7 $42.74   6.458%   $45.5001   $45.50   $45.50   $45.50  
  7 purchase totals = $967.00       $1,036.6260   $1,036.63   $1,036.60   $1,036.60