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	$198.58	5.861%	$210.2188	$210.22	$210.20	$210.20
Purchase #2	$118.76	6.591%	$126.5875	$126.59	$126.60	$126.60
Purchase #3	$229.75	12.816%	$259.1948	$259.19	$259.20	$259.20
Purchase #4	$179.39	11.768%	$200.5006	$200.50	$200.50	$200.50
Purchase #5	$167.79	10.585%	$185.5506	$185.55	$185.55	$185.60
Purchase #6	$52.53	3.364%	$54.2971	$54.30	$54.30	$54.30
Purchase #7	$34.43	13.459%	$39.0639	$39.06	$39.05	$39.10
7 purchase totals =	$981.23		$1,075.4133	$1,075.41	$1,075.40	$1,075.50