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 $119.36   5.331%   $125.7231   $125.72   $125.70   $125.70  
  Purchase #2 $71.65   7.220%   $76.8231   $76.82   $76.80   $76.80  
  Purchase #3 $149.95   7.149%   $160.6699   $160.67   $160.65   $160.70  
  Purchase #4 $61.46   3.221%   $63.4396   $63.44   $63.45   $63.40  
  Purchase #5 $26.32   12.737%   $29.6724   $29.67   $29.65   $29.70  
  Purchase #6 $246.90   12.246%   $277.1354   $277.14   $277.15   $277.10  
  Purchase #7 $75.38   9.847%   $82.8027   $82.80   $82.80   $82.80  
  7 purchase totals = $751.02       $816.2662   $816.26   $816.20   $816.20