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 $70.61   7.596%   $75.9735   $75.97   $75.95   $76.00  
  Purchase #2 $186.38   10.832%   $206.5687   $206.57   $206.55   $206.60  
  Purchase #3 $216.65   8.471%   $235.0024   $235.00   $235.00   $235.00  
  Purchase #4 $66.64   4.301%   $69.5062   $69.51   $69.50   $69.50  
  Purchase #5 $249.27   3.197%   $257.2392   $257.24   $257.25   $257.20  
  Purchase #6 $198.85   11.189%   $221.0993   $221.10   $221.10   $221.10  
  Purchase #7 $9.30   4.501%   $9.7186   $9.72   $9.70   $9.70  
  7 purchase totals = $997.70       $1,075.1079   $1,075.11   $1,075.05   $1,075.10