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 $66.84   4.151%   $69.6145   $69.61   $69.60   $69.60  
  Purchase #2 $236.75   3.123%   $244.1437   $244.14   $244.15   $244.10  
  Purchase #3 $202.87   4.302%   $211.5975   $211.60   $211.60   $211.60  
  Purchase #4 $110.52   3.857%   $114.7828   $114.78   $114.80   $114.80  
  Purchase #5 $61.38   12.874%   $69.2821   $69.28   $69.30   $69.30  
  Purchase #6 $194.91   11.380%   $217.0908   $217.09   $217.10   $217.10  
  Purchase #7 $98.91   12.265%   $111.0413   $111.04   $111.05   $111.00  
  7 purchase totals = $972.18       $1,037.5527   $1,037.54   $1,037.60   $1,037.50