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	$250.98	6.285%	$266.7541	$266.75	$266.75	$266.80
Purchase #2	$219.79	3.394%	$227.2497	$227.25	$227.25	$227.20
Purchase #3	$51.87	5.161%	$54.547	$54.55	$54.55	$54.50
Purchase #4	$145.91	6.743%	$155.7487	$155.75	$155.75	$155.70
Purchase #5	$164.58	13.742%	$187.1966	$187.20	$187.20	$187.20
Purchase #6	$158.86	8.587%	$172.5013	$172.50	$172.50	$172.50
Purchase #7	$83.76	7.816%	$90.3067	$90.31	$90.30	$90.30
7 purchase totals =	$1,075.75		$1,154.3041	$1,154.31	$1,154.30	$1,154.20