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 $119.66   5.475%   $126.2114   $126.21   $126.20   $126.20  
  Purchase #2 $113.35   11.644%   $126.5485   $126.55   $126.55   $126.50  
  Purchase #3 $55.87   9.251%   $61.0385   $61.04   $61.05   $61.00  
  Purchase #4 $168.30   9.624%   $184.4972   $184.50   $184.50   $184.50  
  Purchase #5 $228.78   7.576%   $246.1124   $246.11   $246.10   $246.10  
  Purchase #6 $95.62   12.166%   $107.2531   $107.25   $107.25   $107.30  
  Purchase #7 $142.88   6.309%   $151.8943   $151.89   $151.90   $151.90  
  7 purchase totals = $924.46       $1,003.5554   $1,003.55   $1,003.55   $1,003.50