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	$64.91	10.780%	$71.9073	$71.91	$71.90	$71.90
Purchase #2	$148.96	9.864%	$163.6534	$163.65	$163.65	$163.70
Purchase #3	$184.29	3.205%	$190.1965	$190.20	$190.20	$190.20
Purchase #4	$43.72	4.265%	$45.5847	$45.58	$45.60	$45.60
Purchase #5	$211.78	10.156%	$233.2884	$233.29	$233.30	$233.30
Purchase #6	$71.43	7.365%	$76.6908	$76.69	$76.70	$76.70
Purchase #7	$48.62	11.742%	$54.329	$54.33	$54.35	$54.30
7 purchase totals =	$773.71		$835.6501	$835.65	$835.70	$835.70