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 $119.65   5.318%   $126.013   $126.01   $126.00   $126.00  
  Purchase #2 $126.39   11.110%   $140.4319   $140.43   $140.45   $140.40  
  Purchase #3 $236.80   5.663%   $250.21   $250.21   $250.20   $250.20  
  Purchase #4 $103.69   5.783%   $109.6864   $109.69   $109.70   $109.70  
  Purchase #5 $43.41   4.226%   $45.2445   $45.24   $45.25   $45.20  
  Purchase #6 $250.82   11.673%   $280.0982   $280.10   $280.10   $280.10  
  Purchase #7 $106.56   10.560%   $117.8127   $117.81   $117.80   $117.80  
  7 purchase totals = $987.32       $1,069.4967   $1,069.49   $1,069.50   $1,069.40