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	$63.47	8.570%	$68.9094	$68.91	$68.90	$68.90
Purchase #2	$151.49	4.608%	$158.4707	$158.47	$158.45	$158.50
Purchase #3	$190.43	7.845%	$205.3692	$205.37	$205.35	$205.40
Purchase #4	$19.48	11.719%	$21.7629	$21.76	$21.75	$21.80
Purchase #5	$161.42	12.711%	$181.9381	$181.94	$181.95	$181.90
Purchase #6	$134.89	5.397%	$142.17	$142.17	$142.15	$142.20
Purchase #7	$245.54	9.258%	$268.2721	$268.27	$268.25	$268.30
7 purchase totals =	$966.72		$1,046.8924	$1,046.89	$1,046.80	$1,047.00