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 $96.46   9.227%   $105.3604   $105.36   $105.35   $105.40  
  Purchase #2 $186.71   4.232%   $194.6116   $194.61   $194.60   $194.60  
  Purchase #3 $182.35   12.646%   $205.41   $205.41   $205.40   $205.40  
  Purchase #4 $230.43   9.593%   $252.5351   $252.54   $252.55   $252.50  
  Purchase #5 $84.80   9.260%   $92.6525   $92.65   $92.65   $92.70  
  Purchase #6 $173.30   5.734%   $183.237   $183.24   $183.25   $183.20  
  Purchase #7 $14.30   10.244%   $15.7649   $15.76   $15.75   $15.80  
  7 purchase totals = $968.35       $1,049.5715   $1,049.57   $1,049.55   $1,049.60