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 $176.76   10.855%   $195.9473   $195.95   $195.95   $195.90  
  Purchase #2 $31.38   5.251%   $33.0278   $33.03   $33.05   $33.00  
  Purchase #3 $157.75   12.276%   $177.1154   $177.12   $177.10   $177.10  
  Purchase #4 $17.33   8.324%   $18.7725   $18.77   $18.75   $18.80  
  Purchase #5 $224.93   7.396%   $241.5658   $241.57   $241.55   $241.60  
  Purchase #6 $124.91   13.605%   $141.904   $141.90   $141.90   $141.90  
  Purchase #7 $193.45   7.134%   $207.2507   $207.25   $207.25   $207.30  
  7 purchase totals = $926.51       $1,015.5835   $1,015.59   $1,015.55   $1,015.60