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	$237.49	9.849%	$260.8804	$260.88	$260.90	$260.90
Purchase #2	$179.44	7.287%	$192.5158	$192.52	$192.50	$192.50
Purchase #3	$101.41	13.811%	$115.4157	$115.42	$115.40	$115.40
Purchase #4	$172.74	4.238%	$180.0607	$180.06	$180.05	$180.10
Purchase #5	$118.50	6.672%	$126.4063	$126.41	$126.40	$126.40
Purchase #6	$124.59	6.342%	$132.4915	$132.49	$132.50	$132.50
Purchase #7	$99.55	12.241%	$111.7359	$111.74	$111.75	$111.70
7 purchase totals =	$1,033.72		$1,119.5063	$1,119.52	$1,119.50	$1,119.50