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	$162.29	13.307%	$183.8859	$183.89	$183.90	$183.90
Purchase #2	$225.95	12.414%	$253.9994	$254.00	$254.00	$254.00
Purchase #3	$185.90	5.754%	$196.5967	$196.60	$196.60	$196.60
Purchase #4	$6.65	12.509%	$7.4818	$7.48	$7.50	$7.50
Purchase #5	$209.60	10.362%	$231.3188	$231.32	$231.30	$231.30
Purchase #6	$98.72	12.859%	$111.4144	$111.41	$111.40	$111.40
Purchase #7	$196.88	13.747%	$223.9451	$223.95	$223.95	$223.90
7 purchase totals =	$1,085.99		$1,208.6421	$1,208.65	$1,208.65	$1,208.60