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 $208.36   13.255%   $235.9781   $235.98   $236.00   $236.00  
  Purchase #2 $199.82   7.372%   $214.5507   $214.55   $214.55   $214.60  
  Purchase #3 $48.33   9.166%   $52.7599   $52.76   $52.75   $52.80  
  Purchase #4 $52.40   9.274%   $57.2596   $57.26   $57.25   $57.30  
  Purchase #5 $136.73   11.714%   $152.7466   $152.75   $152.75   $152.70  
  Purchase #6 $174.88   4.543%   $182.8248   $182.82   $182.80   $182.80  
  Purchase #7 $148.46   10.279%   $163.7202   $163.72   $163.70   $163.70  
  7 purchase totals = $968.98       $1,059.8399   $1,059.84   $1,059.80   $1,059.90