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 $181.38   8.420%   $196.6522   $196.65   $196.65   $196.70  
  Purchase #2 $62.84   9.153%   $68.5917   $68.59   $68.60   $68.60  
  Purchase #3 $207.57   8.144%   $224.4745   $224.47   $224.45   $224.50  
  Purchase #4 $35.51   5.501%   $37.4634   $37.46   $37.45   $37.50  
  Purchase #5 $182.25   7.253%   $195.4686   $195.47   $195.45   $195.50  
  Purchase #6 $181.92   8.413%   $197.2249   $197.22   $197.20   $197.20  
  Purchase #7 $245.69   6.160%   $260.8245   $260.82   $260.80   $260.80  
  7 purchase totals = $1,097.16       $1,180.6998   $1,180.68   $1,180.60   $1,180.80