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 $136.71   11.725%   $152.7392   $152.74   $152.75   $152.70  
  Purchase #2 $216.83   12.721%   $244.4129   $244.41   $244.40   $244.40  
  Purchase #3 $94.55   12.645%   $106.5058   $106.51   $106.50   $106.50  
  Purchase #4 $209.28   13.141%   $236.7815   $236.78   $236.80   $236.80  
  Purchase #5 $228.66   4.778%   $239.5854   $239.59   $239.60   $239.60  
  Purchase #6 $35.41   5.816%   $37.4694   $37.47   $37.45   $37.50  
  Purchase #7 $26.27   4.743%   $27.516   $27.52   $27.50   $27.50  
  7 purchase totals = $947.71       $1,045.0102   $1,045.02   $1,045.00   $1,045.00