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 $250.68   7.429%   $269.303   $269.30   $269.30   $269.30  
  Purchase #2 $34.84   4.291%   $36.335   $36.34   $36.35   $36.30  
  Purchase #3 $71.50   7.675%   $76.9876   $76.99   $77.00   $77.00  
  Purchase #4 $176.32   12.193%   $197.8187   $197.82   $197.80   $197.80  
  Purchase #5 $171.73   3.219%   $177.258   $177.26   $177.25   $177.30  
  Purchase #6 $54.81   6.671%   $58.4664   $58.47   $58.45   $58.50  
  Purchase #7 $219.79   8.208%   $237.8304   $237.83   $237.85   $237.80  
  7 purchase totals = $979.67       $1,053.9991   $1,054.01   $1,054.00   $1,054.00