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 $60.85   7.765%   $65.575   $65.58   $65.60   $65.60  
  Purchase #2 $215.69   4.571%   $225.5492   $225.55   $225.55   $225.50  
  Purchase #3 $206.51   7.821%   $222.6611   $222.66   $222.65   $222.70  
  Purchase #4 $194.54   4.484%   $203.2632   $203.26   $203.25   $203.30  
  Purchase #5 $247.40   13.845%   $281.6525   $281.65   $281.65   $281.70  
  Purchase #6 $6.80   12.381%   $7.6419   $7.64   $7.65   $7.60  
  Purchase #7 $162.30   5.749%   $171.6306   $171.63   $171.65   $171.60  
  7 purchase totals = $1,094.09       $1,177.9735   $1,177.97   $1,178.00   $1,178.00