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	$60.80	9.308%	$66.4593	$66.46	$66.45	$66.50
Purchase #2	$140.71	7.706%	$151.5531	$151.55	$151.55	$151.60
Purchase #3	$94.51	6.269%	$100.4348	$100.43	$100.45	$100.40
Purchase #4	$205.67	9.161%	$224.5114	$224.51	$224.50	$224.50
Purchase #5	$175.83	11.796%	$196.5709	$196.57	$196.55	$196.60
Purchase #6	$176.31	4.789%	$184.7535	$184.75	$184.75	$184.80
Purchase #7	$163.61	9.845%	$179.7174	$179.72	$179.70	$179.70
7 purchase totals =	$1,017.44		$1,104.0004	$1,103.99	$1,103.95	$1,104.10