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 $169.81   13.816%   $193.2709   $193.27   $193.25   $193.30  
  Purchase #2 $171.64   13.762%   $195.2611   $195.26   $195.25   $195.30  
  Purchase #3 $170.57   8.808%   $185.5938   $185.59   $185.60   $185.60  
  Purchase #4 $62.71   3.564%   $64.945   $64.95   $64.95   $64.90  
  Purchase #5 $110.65   3.850%   $114.91   $114.91   $114.90   $114.90  
  Purchase #6 $150.75   11.829%   $168.5822   $168.58   $168.60   $168.60  
  Purchase #7 $145.58   3.871%   $151.2154   $151.22   $151.20   $151.20  
  7 purchase totals = $981.71       $1,073.7784   $1,073.78   $1,073.75   $1,073.80