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 $182.39   11.269%   $202.9435   $202.94   $202.95   $202.90  
  Purchase #2 $62.45   13.614%   $70.9519   $70.95   $70.95   $71.00  
  Purchase #3 $82.48   10.661%   $91.2732   $91.27   $91.25   $91.30  
  Purchase #4 $159.83   8.675%   $173.6953   $173.70   $173.70   $173.70  
  Purchase #5 $225.78   4.452%   $235.8317   $235.83   $235.85   $235.80  
  Purchase #6 $57.93   5.147%   $60.9117   $60.91   $60.90   $60.90  
  Purchase #7 $215.46   11.828%   $240.9446   $240.94   $240.95   $240.90  
  7 purchase totals = $986.32       $1,076.5519   $1,076.54   $1,076.55   $1,076.50