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 $42.55   10.127%   $46.859   $46.86   $46.85   $46.90  
  Purchase #2 $114.79   8.552%   $124.6068   $124.61   $124.60   $124.60  
  Purchase #3 $113.76   3.451%   $117.6859   $117.69   $117.70   $117.70  
  Purchase #4 $231.45   4.515%   $241.9   $241.90   $241.90   $241.90  
  Purchase #5 $147.90   9.399%   $161.8011   $161.80   $161.80   $161.80  
  Purchase #6 $198.91   10.392%   $219.5807   $219.58   $219.60   $219.60  
  Purchase #7 $141.78   5.539%   $149.6332   $149.63   $149.65   $149.60  
  7 purchase totals = $991.14       $1,062.0667   $1,062.07   $1,062.10   $1,062.10