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 $228.80   13.750%   $260.26   $260.26   $260.25   $260.30  
  Purchase #2 $219.63   11.857%   $245.6715   $245.67   $245.65   $245.70  
  Purchase #3 $96.38   5.466%   $101.6481   $101.65   $101.65   $101.60  
  Purchase #4 $161.78   5.344%   $170.4255   $170.43   $170.45   $170.40  
  Purchase #5 $179.72   9.497%   $196.788   $196.79   $196.80   $196.80  
  Purchase #6 $95.59   10.176%   $105.3172   $105.32   $105.30   $105.30  
  Purchase #7 $23.73   5.740%   $25.0921   $25.09   $25.10   $25.10  
  7 purchase totals = $1,005.63       $1,105.2024   $1,105.21   $1,105.20   $1,105.20