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 $46.67   5.720%   $49.3395   $49.34   $49.35   $49.30  
  Purchase #2 $113.26   8.465%   $122.8475   $122.85   $122.85   $122.80  
  Purchase #3 $188.43   11.656%   $210.3934   $210.39   $210.40   $210.40  
  Purchase #4 $161.38   7.595%   $173.6368   $173.64   $173.65   $173.60  
  Purchase #5 $247.54   5.369%   $260.8304   $260.83   $260.85   $260.80  
  Purchase #6 $114.61   3.183%   $118.258   $118.26   $118.25   $118.30  
  Purchase #7 $118.82   11.760%   $132.7932   $132.79   $132.80   $132.80  
  7 purchase totals = $990.71       $1,068.0988   $1,068.10   $1,068.15   $1,068.00