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 $196.64   6.616%   $209.6497   $209.65   $209.65   $209.60  
  Purchase #2 $174.76   12.497%   $196.5998   $196.60   $196.60   $196.60  
  Purchase #3 $32.44   4.619%   $33.9384   $33.94   $33.95   $33.90  
  Purchase #4 $119.34   13.354%   $135.2767   $135.28   $135.30   $135.30  
  Purchase #5 $216.48   12.538%   $243.6223   $243.62   $243.60   $243.60  
  Purchase #6 $21.43   13.570%   $24.3381   $24.34   $24.35   $24.30  
  Purchase #7 $204.54   10.702%   $226.4299   $226.43   $226.45   $226.40  
  7 purchase totals = $965.63       $1,069.8549   $1,069.86   $1,069.90   $1,069.70