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	$214.66	12.192%	$240.8313	$240.83	$240.85	$240.80
Purchase #2	$131.39	13.691%	$149.3786	$149.38	$149.40	$149.40
Purchase #3	$155.52	8.539%	$168.7999	$168.80	$168.80	$168.80
Purchase #4	$80.42	11.552%	$89.7101	$89.71	$89.70	$89.70
Purchase #5	$119.25	9.599%	$130.6968	$130.70	$130.70	$130.70
Purchase #6	$74.30	5.230%	$78.1859	$78.19	$78.20	$78.20
Purchase #7	$184.38	8.826%	$200.6534	$200.65	$200.65	$200.70
7 purchase totals =	$959.92		$1,058.2560	$1,058.26	$1,058.30	$1,058.30