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	$52.67	12.431%	$59.2174	$59.22	$59.20	$59.20
Purchase #2	$51.75	6.273%	$54.9963	$55.00	$55.00	$55.00
Purchase #3	$35.43	9.872%	$38.9276	$38.93	$38.95	$38.90
Purchase #4	$71.84	8.649%	$78.0534	$78.05	$78.05	$78.10
Purchase #5	$248.49	9.491%	$272.0742	$272.07	$272.05	$272.10
Purchase #6	$49.49	10.439%	$54.6563	$54.66	$54.65	$54.70
Purchase #7	$116.59	12.494%	$131.1568	$131.16	$131.15	$131.20
7 purchase totals =	$626.26		$689.0820	$689.09	$689.05	$689.20