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 $58.81   5.402%   $61.9869   $61.99   $62.00   $62.00  
  Purchase #2 $35.87   5.322%   $37.779   $37.78   $37.80   $37.80  
  Purchase #3 $183.72   4.572%   $192.1197   $192.12   $192.10   $192.10  
  Purchase #4 $14.56   10.488%   $16.0871   $16.09   $16.10   $16.10  
  Purchase #5 $162.42   5.611%   $171.5334   $171.53   $171.55   $171.50  
  Purchase #6 $16.45   5.425%   $17.3424   $17.34   $17.35   $17.30  
  Purchase #7 $56.86   8.476%   $61.6795   $61.68   $61.70   $61.70  
  7 purchase totals = $528.69       $558.5280   $558.53   $558.60   $558.50