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	$140.79	11.704%	$157.2681	$157.27	$157.25	$157.30
Purchase #2	$178.68	8.858%	$194.5075	$194.51	$194.50	$194.50
Purchase #3	$207.72	4.293%	$216.6374	$216.64	$216.65	$216.60
Purchase #4	$12.77	12.799%	$14.4044	$14.40	$14.40	$14.40
Purchase #5	$55.85	5.146%	$58.724	$58.72	$58.70	$58.70
Purchase #6	$98.61	13.131%	$111.5585	$111.56	$111.55	$111.60
Purchase #7	$205.82	4.647%	$215.3845	$215.38	$215.40	$215.40
7 purchase totals =	$900.24		$968.4844	$968.48	$968.45	$968.50