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 $192.66   4.674%   $201.6649   $201.66   $201.65   $201.70  
  Purchase #2 $215.55   5.593%   $227.6057   $227.61   $227.60   $227.60  
  Purchase #3 $87.90   6.588%   $93.6909   $93.69   $93.70   $93.70  
  Purchase #4 $6.86   12.613%   $7.7253   $7.73   $7.75   $7.70  
  Purchase #5 $128.95   10.187%   $142.0861   $142.09   $142.10   $142.10  
  Purchase #6 $206.59   5.645%   $218.252   $218.25   $218.25   $218.30  
  Purchase #7 $21.56   9.381%   $23.5825   $23.58   $23.60   $23.60  
  7 purchase totals = $860.07       $914.6074   $914.61   $914.65   $914.70