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 $204.83   3.334%   $211.659   $211.66   $211.65   $211.70  
  Purchase #2 $207.72   5.217%   $218.5568   $218.56   $218.55   $218.60  
  Purchase #3 $53.69   10.187%   $59.1594   $59.16   $59.15   $59.20  
  Purchase #4 $218.35   8.444%   $236.7875   $236.79   $236.80   $236.80  
  Purchase #5 $58.61   6.178%   $62.2309   $62.23   $62.25   $62.20  
  Purchase #6 $196.35   5.156%   $206.4738   $206.47   $206.45   $206.50  
  Purchase #7 $154.70   5.510%   $163.224   $163.22   $163.20   $163.20  
  7 purchase totals = $1,094.25       $1,158.0914   $1,158.09   $1,158.05   $1,158.20