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	$212.71	4.638%	$222.5755	$222.58	$222.60	$222.60
Purchase #2	$12.36	9.167%	$13.493	$13.49	$13.50	$13.50
Purchase #3	$18.52	9.694%	$20.3153	$20.32	$20.30	$20.30
Purchase #4	$210.39	9.121%	$229.5797	$229.58	$229.60	$229.60
Purchase #5	$223.60	6.651%	$238.4716	$238.47	$238.45	$238.50
Purchase #6	$20.35	3.708%	$21.1046	$21.10	$21.10	$21.10
Purchase #7	$184.74	12.868%	$208.5123	$208.51	$208.50	$208.50
7 purchase totals =	$882.67		$954.0520	$954.05	$954.05	$954.10