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 $57.55   8.815%   $62.623   $62.62   $62.60   $62.60  
  Purchase #2 $114.64   7.638%   $123.3962   $123.40   $123.40   $123.40  
  Purchase #3 $187.76   6.315%   $199.617   $199.62   $199.60   $199.60  
  Purchase #4 $113.38   8.776%   $123.3302   $123.33   $123.35   $123.30  
  Purchase #5 $186.58   11.257%   $207.5833   $207.58   $207.60   $207.60  
  Purchase #6 $98.89   11.485%   $110.2475   $110.25   $110.25   $110.20  
  Purchase #7 $213.90   10.598%   $236.5691   $236.57   $236.55   $236.60  
  7 purchase totals = $972.70       $1,063.3663   $1,063.37   $1,063.35   $1,063.30