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 $61.77   13.403%   $70.049   $70.05   $70.05   $70.00  
  Purchase #2 $239.44   7.800%   $258.1163   $258.12   $258.10   $258.10  
  Purchase #3 $213.86   9.286%   $233.719   $233.72   $233.70   $233.70  
  Purchase #4 $15.41   5.787%   $16.3018   $16.30   $16.30   $16.30  
  Purchase #5 $198.79   3.393%   $205.5349   $205.53   $205.55   $205.50  
  Purchase #6 $157.88   7.285%   $169.3816   $169.38   $169.40   $169.40  
  Purchase #7 $12.54   11.287%   $13.9554   $13.96   $13.95   $14.00  
  7 purchase totals = $899.69       $967.0580   $967.06   $967.05   $967.00