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 $69.87   5.431%   $73.6646   $73.66   $73.65   $73.70  
  Purchase #2 $143.64   3.404%   $148.5295   $148.53   $148.55   $148.50  
  Purchase #3 $242.36   4.301%   $252.7839   $252.78   $252.80   $252.80  
  Purchase #4 $191.73   10.241%   $211.3651   $211.37   $211.35   $211.40  
  Purchase #5 $183.79   3.489%   $190.2024   $190.20   $190.20   $190.20  
  Purchase #6 $209.54   5.403%   $220.8614   $220.86   $220.85   $220.90  
  Purchase #7 $55.78   4.358%   $58.2109   $58.21   $58.20   $58.20  
  7 purchase totals = $1,096.71       $1,155.6178   $1,155.61   $1,155.60   $1,155.70