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	$233.43	13.596%	$265.1671	$265.17	$265.15	$265.20
Purchase #2	$27.52	4.392%	$28.7287	$28.73	$28.75	$28.70
Purchase #3	$47.93	13.159%	$54.2371	$54.24	$54.25	$54.20
Purchase #4	$101.32	4.358%	$105.7355	$105.74	$105.75	$105.70
Purchase #5	$155.70	4.411%	$162.5679	$162.57	$162.55	$162.60
Purchase #6	$139.25	4.307%	$145.2475	$145.25	$145.25	$145.20
Purchase #7	$40.32	8.180%	$43.6182	$43.62	$43.60	$43.60
7 purchase totals =	$745.47		$805.3020	$805.32	$805.30	$805.20