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 $60.38   5.663%   $63.7993   $63.80   $63.80   $63.80  
  Purchase #2 $154.91   4.834%   $162.3983   $162.40   $162.40   $162.40  
  Purchase #3 $99.35   13.623%   $112.8845   $112.88   $112.90   $112.90  
  Purchase #4 $68.61   3.723%   $71.1644   $71.16   $71.15   $71.20  
  Purchase #5 $247.99   3.302%   $256.1786   $256.18   $256.20   $256.20  
  Purchase #6 $222.69   3.449%   $230.3706   $230.37   $230.35   $230.40  
  Purchase #7 $112.78   11.739%   $126.0192   $126.02   $126.00   $126.00  
  7 purchase totals = $966.71       $1,022.8149   $1,022.81   $1,022.80   $1,022.90