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	$182.66	11.397%	$203.4778	$203.48	$203.50	$203.50
Purchase #2	$13.54	11.357%	$15.0777	$15.08	$15.10	$15.10
Purchase #3	$72.51	12.542%	$81.6042	$81.60	$81.60	$81.60
Purchase #4	$179.71	3.176%	$185.4176	$185.42	$185.40	$185.40
Purchase #5	$102.61	6.244%	$109.017	$109.02	$109.00	$109.00
Purchase #6	$89.58	4.256%	$93.3925	$93.39	$93.40	$93.40
Purchase #7	$97.35	12.528%	$109.546	$109.55	$109.55	$109.50
7 purchase totals =	$737.96		$797.5328	$797.54	$797.55	$797.50