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 $241.83   7.790%   $260.6686   $260.67   $260.65   $260.70  
  Purchase #2 $148.41   10.612%   $164.1593   $164.16   $164.15   $164.20  
  Purchase #3 $183.82   6.230%   $195.272   $195.27   $195.25   $195.30  
  Purchase #4 $229.45   7.445%   $246.5326   $246.53   $246.55   $246.50  
  Purchase #5 $69.47   4.459%   $72.5677   $72.57   $72.55   $72.60  
  Purchase #6 $43.41   8.466%   $47.0851   $47.09   $47.10   $47.10  
  Purchase #7 $71.67   5.752%   $75.7925   $75.79   $75.80   $75.80  
  7 purchase totals = $988.06       $1,062.0778   $1,062.08   $1,062.05   $1,062.20