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	$130.46	13.835%	$148.5091	$148.51	$148.50	$148.50
Purchase #2	$111.84	10.174%	$123.2186	$123.22	$123.20	$123.20
Purchase #3	$132.35	9.354%	$144.73	$144.73	$144.75	$144.70
Purchase #4	$233.60	3.488%	$241.748	$241.75	$241.75	$241.70
Purchase #5	$185.99	13.627%	$211.3349	$211.33	$211.35	$211.30
Purchase #6	$131.94	4.813%	$138.2903	$138.29	$138.30	$138.30
Purchase #7	$61.36	9.499%	$67.1886	$67.19	$67.20	$67.20
7 purchase totals =	$987.54		$1,075.0195	$1,075.02	$1,075.05	$1,074.90