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 $192.69   5.243%   $202.7927   $202.79   $202.80   $202.80  
  Purchase #2 $175.45   13.246%   $198.6901   $198.69   $198.70   $198.70  
  Purchase #3 $191.86   3.137%   $197.8786   $197.88   $197.90   $197.90  
  Purchase #4 $34.56   3.434%   $35.7468   $35.75   $35.75   $35.70  
  Purchase #5 $136.93   3.476%   $141.6897   $141.69   $141.70   $141.70  
  Purchase #6 $68.29   4.376%   $71.2784   $71.28   $71.30   $71.30  
  Purchase #7 $105.48   12.390%   $118.549   $118.55   $118.55   $118.50  
  7 purchase totals = $905.26       $966.6253   $966.63   $966.70   $966.60