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 $126.95   5.764%   $134.2674   $134.27   $134.25   $134.30  
  Purchase #2 $184.43   11.833%   $206.2536   $206.25   $206.25   $206.30  
  Purchase #3 $173.67   8.284%   $188.0568   $188.06   $188.05   $188.10  
  Purchase #4 $97.84   8.468%   $106.1251   $106.13   $106.15   $106.10  
  Purchase #5 $58.58   10.571%   $64.7725   $64.77   $64.75   $64.80  
  Purchase #6 $118.91   3.352%   $122.8959   $122.90   $122.90   $122.90  
  Purchase #7 $176.31   12.715%   $198.7278   $198.73   $198.75   $198.70  
  7 purchase totals = $936.69       $1,021.0991   $1,021.11   $1,021.10   $1,021.20