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 $151.58   11.473%   $168.9708   $168.97   $168.95   $169.00  
  Purchase #2 $174.79   12.131%   $195.9938   $195.99   $196.00   $196.00  
  Purchase #3 $230.92   9.505%   $252.8689   $252.87   $252.85   $252.90  
  Purchase #4 $208.45   3.176%   $215.0704   $215.07   $215.05   $215.10  
  Purchase #5 $207.34   6.820%   $221.4806   $221.48   $221.50   $221.50  
  Purchase #6 $33.42   8.480%   $36.254   $36.25   $36.25   $36.30  
  Purchase #7 $106.27   13.146%   $120.2403   $120.24   $120.25   $120.20  
  7 purchase totals = $1,112.77       $1,210.8788   $1,210.87   $1,210.85   $1,211.00