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 $191.27   7.544%   $205.6994   $205.70   $205.70   $205.70  
  Purchase #2 $71.89   6.809%   $76.785   $76.79   $76.80   $76.80  
  Purchase #3 $152.69   7.779%   $164.5678   $164.57   $164.55   $164.60  
  Purchase #4 $137.91   8.412%   $149.511   $149.51   $149.50   $149.50  
  Purchase #5 $211.70   11.588%   $236.2318   $236.23   $236.25   $236.20  
  Purchase #6 $164.40   9.649%   $180.263   $180.26   $180.25   $180.30  
  Purchase #7 $207.52   3.247%   $214.2582   $214.26   $214.25   $214.30  
  7 purchase totals = $1,137.38       $1,227.3162   $1,227.32   $1,227.30   $1,227.40