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 $71.61   6.135%   $76.0033   $76.00   $76.00   $76.00  
  Purchase #2 $242.55   12.376%   $272.568   $272.57   $272.55   $272.60  
  Purchase #3 $55.88   12.851%   $63.0611   $63.06   $63.05   $63.10  
  Purchase #4 $131.37   7.573%   $141.3187   $141.32   $141.30   $141.30  
  Purchase #5 $88.34   9.770%   $96.9708   $96.97   $96.95   $97.00  
  Purchase #6 $162.91   7.506%   $175.138   $175.14   $175.15   $175.10  
  Purchase #7 $43.51   13.140%   $49.2272   $49.23   $49.25   $49.20  
  7 purchase totals = $796.17       $874.2871   $874.29   $874.25   $874.30