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 $211.38   6.410%   $224.9295   $224.93   $224.95   $224.90  
  Purchase #2 $68.27   4.445%   $71.3046   $71.30   $71.30   $71.30  
  Purchase #3 $249.72   4.705%   $261.4693   $261.47   $261.45   $261.50  
  Purchase #4 $164.66   11.757%   $184.0191   $184.02   $184.00   $184.00  
  Purchase #5 $227.91   3.120%   $235.0208   $235.02   $235.00   $235.00  
  Purchase #6 $111.40   6.298%   $118.416   $118.42   $118.40   $118.40  
  Purchase #7 $46.42   11.389%   $51.7068   $51.71   $51.70   $51.70  
  7 purchase totals = $1,079.76       $1,146.8661   $1,146.87   $1,146.80   $1,146.80