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 $113.27   9.568%   $124.1077   $124.11   $124.10   $124.10  
  Purchase #2 $248.61   10.187%   $273.9359   $273.94   $273.95   $273.90  
  Purchase #3 $143.47   12.245%   $161.0379   $161.04   $161.05   $161.00  
  Purchase #4 $15.66   12.733%   $17.654   $17.65   $17.65   $17.70  
  Purchase #5 $152.93   12.614%   $172.2206   $172.22   $172.20   $172.20  
  Purchase #6 $202.84   13.606%   $230.4384   $230.44   $230.45   $230.40  
  Purchase #7 $68.59   8.233%   $74.237   $74.24   $74.25   $74.20  
  7 purchase totals = $945.37       $1,053.6315   $1,053.64   $1,053.65   $1,053.50