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 $182.98   13.657%   $207.9696   $207.97   $207.95   $208.00  
  Purchase #2 $57.30   8.292%   $62.0513   $62.05   $62.05   $62.10  
  Purchase #3 $230.98   8.774%   $251.2462   $251.25   $251.25   $251.20  
  Purchase #4 $141.90   3.795%   $147.2851   $147.29   $147.30   $147.30  
  Purchase #5 $162.93   11.246%   $181.2531   $181.25   $181.25   $181.30  
  Purchase #6 $242.52   6.334%   $257.8812   $257.88   $257.90   $257.90  
  Purchase #7 $53.98   5.271%   $56.8253   $56.83   $56.85   $56.80  
  7 purchase totals = $1,072.59       $1,164.5118   $1,164.52   $1,164.55   $1,164.60