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 $195.64   8.371%   $212.017   $212.02   $212.00   $212.00  
  Purchase #2 $24.76   5.464%   $26.1129   $26.11   $26.10   $26.10  
  Purchase #3 $190.90   9.247%   $208.5525   $208.55   $208.55   $208.60  
  Purchase #4 $123.49   13.461%   $140.113   $140.11   $140.10   $140.10  
  Purchase #5 $63.50   9.856%   $69.7586   $69.76   $69.75   $69.80  
  Purchase #6 $189.70   13.774%   $215.8293   $215.83   $215.85   $215.80  
  Purchase #7 $197.83   10.543%   $218.6872   $218.69   $218.70   $218.70  
  7 purchase totals = $985.82       $1,091.0705   $1,091.07   $1,091.05   $1,091.10