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 $119.78   5.699%   $126.6063   $126.61   $126.60   $126.60  
  Purchase #2 $201.82   13.351%   $228.765   $228.77   $228.75   $228.80  
  Purchase #3 $211.57   4.568%   $221.2345   $221.23   $221.25   $221.20  
  Purchase #4 $49.95   8.633%   $54.2622   $54.26   $54.25   $54.30  
  Purchase #5 $86.48   10.539%   $95.5941   $95.59   $95.60   $95.60  
  Purchase #6 $6.38   9.617%   $6.9936   $6.99   $7.00   $7.00  
  Purchase #7 $148.79   8.737%   $161.7898   $161.79   $161.80   $161.80  
  7 purchase totals = $824.77       $895.2455   $895.24   $895.25   $895.30