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 $118.51   5.476%   $124.9996   $125.00   $125.00   $125.00  
  Purchase #2 $224.87   5.535%   $237.3166   $237.32   $237.30   $237.30  
  Purchase #3 $191.87   4.822%   $201.122   $201.12   $201.10   $201.10  
  Purchase #4 $239.69   8.698%   $260.5382   $260.54   $260.55   $260.50  
  Purchase #5 $60.44   4.322%   $63.0522   $63.05   $63.05   $63.10  
  Purchase #6 $11.61   13.561%   $13.1844   $13.18   $13.20   $13.20  
  Purchase #7 $122.68   7.669%   $132.0883   $132.09   $132.10   $132.10  
  7 purchase totals = $969.67       $1,032.3013   $1,032.30   $1,032.30   $1,032.30