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 $127.31   11.341%   $141.7482   $141.75   $141.75   $141.70  
  Purchase #2 $225.89   4.160%   $235.287   $235.29   $235.30   $235.30  
  Purchase #3 $167.35   12.382%   $188.0713   $188.07   $188.05   $188.10  
  Purchase #4 $21.79   9.116%   $23.7764   $23.78   $23.80   $23.80  
  Purchase #5 $207.40   7.301%   $222.5423   $222.54   $222.55   $222.50  
  Purchase #6 $124.87   13.488%   $141.7125   $141.71   $141.70   $141.70  
  Purchase #7 $85.51   3.235%   $88.2762   $88.28   $88.30   $88.30  
  7 purchase totals = $960.12       $1,041.4139   $1,041.42   $1,041.45   $1,041.40