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 $214.66   4.343%   $223.9827   $223.98   $224.00   $224.00  
  Purchase #2 $117.38   11.326%   $130.6745   $130.67   $130.65   $130.70  
  Purchase #3 $51.91   12.786%   $58.5472   $58.55   $58.55   $58.50  
  Purchase #4 $226.67   4.334%   $236.4939   $236.49   $236.50   $236.50  
  Purchase #5 $175.61   6.653%   $187.2933   $187.29   $187.30   $187.30  
  Purchase #6 $170.87   3.757%   $177.2896   $177.29   $177.30   $177.30  
  Purchase #7 $41.44   9.585%   $45.412   $45.41   $45.40   $45.40  
  7 purchase totals = $998.54       $1,059.6932   $1,059.68   $1,059.70   $1,059.70