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 $178.93   9.320%   $195.6063   $195.61   $195.60   $195.60  
  Purchase #2 $69.55   8.700%   $75.6009   $75.60   $75.60   $75.60  
  Purchase #3 $163.77   8.575%   $177.8133   $177.81   $177.80   $177.80  
  Purchase #4 $223.78   5.450%   $235.976   $235.98   $236.00   $236.00  
  Purchase #5 $140.26   3.331%   $144.9321   $144.93   $144.95   $144.90  
  Purchase #6 $100.88   12.856%   $113.8491   $113.85   $113.85   $113.80  
  Purchase #7 $247.74   5.599%   $261.611   $261.61   $261.60   $261.60  
  7 purchase totals = $1,124.91       $1,205.3887   $1,205.39   $1,205.40   $1,205.30