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 $162.68   11.628%   $181.5964   $181.60   $181.60   $181.60  
  Purchase #2 $122.49   4.338%   $127.8036   $127.80   $127.80   $127.80  
  Purchase #3 $124.62   8.221%   $134.865   $134.87   $134.85   $134.90  
  Purchase #4 $49.69   7.425%   $53.3795   $53.38   $53.40   $53.40  
  Purchase #5 $232.45   13.337%   $263.4519   $263.45   $263.45   $263.50  
  Purchase #6 $45.60   9.508%   $49.9356   $49.94   $49.95   $49.90  
  Purchase #7 $147.36   7.176%   $157.9346   $157.93   $157.95   $157.90  
  7 purchase totals = $884.89       $968.9666   $968.97   $969.00   $969.00