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 $176.82   10.846%   $195.9979   $196.00   $196.00   $196.00  
  Purchase #2 $56.98   9.359%   $62.3128   $62.31   $62.30   $62.30  
  Purchase #3 $77.26   7.413%   $82.9873   $82.99   $83.00   $83.00  
  Purchase #4 $110.81   3.260%   $114.4224   $114.42   $114.40   $114.40  
  Purchase #5 $190.60   5.671%   $201.4089   $201.41   $201.40   $201.40  
  Purchase #6 $18.55   11.166%   $20.6213   $20.62   $20.60   $20.60  
  Purchase #7 $166.76   11.310%   $185.6206   $185.62   $185.60   $185.60  
  7 purchase totals = $797.78       $863.3712   $863.37   $863.30   $863.30