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 $67.84   7.631%   $73.0169   $73.02   $73.00   $73.00  
  Purchase #2 $79.83   5.353%   $84.1033   $84.10   $84.10   $84.10  
  Purchase #3 $145.35   4.401%   $151.7469   $151.75   $151.75   $151.70  
  Purchase #4 $168.87   13.387%   $191.4766   $191.48   $191.50   $191.50  
  Purchase #5 $242.48   8.150%   $262.2421   $262.24   $262.25   $262.20  
  Purchase #6 $170.69   6.774%   $182.2525   $182.25   $182.25   $182.30  
  Purchase #7 $242.25   4.537%   $253.2409   $253.24   $253.25   $253.20  
  7 purchase totals = $1,117.31       $1,198.0792   $1,198.08   $1,198.10   $1,198.00