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 $69.44   10.770%   $76.9187   $76.92   $76.90   $76.90  
  Purchase #2 $249.58   5.123%   $262.366   $262.37   $262.35   $262.40  
  Purchase #3 $17.83   5.778%   $18.8602   $18.86   $18.85   $18.90  
  Purchase #4 $43.94   4.258%   $45.811   $45.81   $45.80   $45.80  
  Purchase #5 $241.48   9.663%   $264.8142   $264.81   $264.80   $264.80  
  Purchase #6 $158.67   13.544%   $180.1603   $180.16   $180.15   $180.20  
  Purchase #7 $193.32   5.242%   $203.4538   $203.45   $203.45   $203.50  
  7 purchase totals = $974.26       $1,052.3842   $1,052.38   $1,052.30   $1,052.50