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 $177.41   10.633%   $196.274   $196.27   $196.25   $196.30  
  Purchase #2 $46.57   11.296%   $51.8305   $51.83   $51.85   $51.80  
  Purchase #3 $49.47   8.271%   $53.5617   $53.56   $53.55   $53.60  
  Purchase #4 $203.33   8.771%   $221.1641   $221.16   $221.15   $221.20  
  Purchase #5 $232.48   10.614%   $257.1554   $257.16   $257.15   $257.20  
  Purchase #6 $51.48   8.804%   $56.0123   $56.01   $56.00   $56.00  
  Purchase #7 $210.57   8.177%   $227.7883   $227.79   $227.80   $227.80  
  7 purchase totals = $971.31       $1,063.7863   $1,063.78   $1,063.75   $1,063.90