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	$99.83	11.657%	$111.4672	$111.47	$111.45	$111.50
Purchase #2	$164.42	13.231%	$186.1744	$186.17	$186.15	$186.20
Purchase #3	$179.33	7.868%	$193.4397	$193.44	$193.45	$193.40
Purchase #4	$11.68	8.381%	$12.6589	$12.66	$12.65	$12.70
Purchase #5	$78.78	10.267%	$86.8683	$86.87	$86.85	$86.90
Purchase #6	$130.50	7.668%	$140.5067	$140.51	$140.50	$140.50
Purchase #7	$96.39	6.486%	$102.6419	$102.64	$102.65	$102.60
7 purchase totals =	$760.93		$833.7571	$833.76	$833.70	$833.80