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 $111.95   6.274%   $118.9737   $118.97   $118.95   $119.00  
  Purchase #2 $168.81   10.421%   $186.4017   $186.40   $186.40   $186.40  
  Purchase #3 $82.26   6.312%   $87.4523   $87.45   $87.45   $87.50  
  Purchase #4 $89.69   12.606%   $100.9963   $101.00   $101.00   $101.00  
  Purchase #5 $180.47   10.823%   $200.0023   $200.00   $200.00   $200.00  
  Purchase #6 $75.51   12.783%   $85.1624   $85.16   $85.15   $85.20  
  Purchase #7 $230.83   6.811%   $246.5518   $246.55   $246.55   $246.60  
  7 purchase totals = $939.52       $1,025.5405   $1,025.53   $1,025.50   $1,025.70