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 $196.80   4.595%   $205.843   $205.84   $205.85   $205.80  
  Purchase #2 $241.55   5.635%   $255.1613   $255.16   $255.15   $255.20  
  Purchase #3 $120.76   4.393%   $126.065   $126.07   $126.05   $126.10  
  Purchase #4 $212.32   3.333%   $219.3966   $219.40   $219.40   $219.40  
  Purchase #5 $11.45   3.329%   $11.8312   $11.83   $11.85   $11.80  
  Purchase #6 $48.26   7.630%   $51.9422   $51.94   $51.95   $51.90  
  Purchase #7 $100.43   11.516%   $111.9955   $112.00   $112.00   $112.00  
  7 purchase totals = $931.57       $982.2348   $982.24   $982.25   $982.20