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	$43.47	9.547%	$47.6201	$47.62	$47.60	$47.60
Purchase #2	$209.83	6.562%	$223.599	$223.60	$223.60	$223.60
Purchase #3	$11.48	8.849%	$12.4959	$12.50	$12.50	$12.50
Purchase #4	$202.57	7.238%	$217.232	$217.23	$217.25	$217.20
Purchase #5	$192.43	12.102%	$215.7179	$215.72	$215.70	$215.70
Purchase #6	$176.58	6.764%	$188.5239	$188.52	$188.50	$188.50
Purchase #7	$171.28	4.203%	$178.4789	$178.48	$178.50	$178.50
7 purchase totals =	$1,007.64		$1,083.6677	$1,083.67	$1,083.65	$1,083.60