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 $67.32   6.804%   $71.9005   $71.90   $71.90   $71.90  
  Purchase #2 $183.29   6.688%   $195.5484   $195.55   $195.55   $195.50  
  Purchase #3 $41.37   3.859%   $42.9665   $42.97   $42.95   $43.00  
  Purchase #4 $106.85   3.280%   $110.3547   $110.35   $110.35   $110.40  
  Purchase #5 $118.56   3.744%   $122.9989   $123.00   $123.00   $123.00  
  Purchase #6 $60.40   13.629%   $68.6319   $68.63   $68.65   $68.60  
  Purchase #7 $150.25   9.508%   $164.5358   $164.54   $164.55   $164.50  
  7 purchase totals = $728.04       $776.9367   $776.94   $776.95   $776.90