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 $68.54   11.268%   $76.2631   $76.26   $76.25   $76.30  
  Purchase #2 $199.95   6.823%   $213.5926   $213.59   $213.60   $213.60  
  Purchase #3 $246.81   9.741%   $270.8518   $270.85   $270.85   $270.90  
  Purchase #4 $138.95   3.506%   $143.8216   $143.82   $143.80   $143.80  
  Purchase #5 $218.68   7.645%   $235.3981   $235.40   $235.40   $235.40  
  Purchase #6 $87.75   6.504%   $93.4573   $93.46   $93.45   $93.50  
  Purchase #7 $218.91   6.679%   $233.531   $233.53   $233.55   $233.50  
  7 purchase totals = $1,179.59       $1,266.9155   $1,266.91   $1,266.90   $1,267.00