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 $182.57   7.496%   $196.2554   $196.26   $196.25   $196.30  
  Purchase #2 $76.47   3.857%   $79.4194   $79.42   $79.40   $79.40  
  Purchase #3 $71.64   4.677%   $74.9906   $74.99   $75.00   $75.00  
  Purchase #4 $174.34   12.678%   $196.4428   $196.44   $196.45   $196.40  
  Purchase #5 $115.59   7.543%   $124.309   $124.31   $124.30   $124.30  
  Purchase #6 $164.41   6.603%   $175.266   $175.27   $175.25   $175.30  
  Purchase #7 $209.27   4.160%   $217.9756   $217.98   $218.00   $218.00  
  7 purchase totals = $994.29       $1,064.6588   $1,064.67   $1,064.65   $1,064.70