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 $162.34   3.771%   $168.4618   $168.46   $168.45   $168.50  
  Purchase #2 $182.81   8.553%   $198.4457   $198.45   $198.45   $198.40  
  Purchase #3 $246.99   7.661%   $265.9119   $265.91   $265.90   $265.90  
  Purchase #4 $223.97   6.445%   $238.4049   $238.40   $238.40   $238.40  
  Purchase #5 $59.81   4.589%   $62.5547   $62.55   $62.55   $62.60  
  Purchase #6 $15.33   4.678%   $16.0471   $16.05   $16.05   $16.00  
  Purchase #7 $103.94   9.313%   $113.6199   $113.62   $113.60   $113.60  
  7 purchase totals = $995.19       $1,063.4460   $1,063.44   $1,063.40   $1,063.40