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	$129.53	3.158%	$133.6206	$133.62	$133.60	$133.60
Purchase #2	$10.91	4.419%	$11.3921	$11.39	$11.40	$11.40
Purchase #3	$9.28	13.444%	$10.5276	$10.53	$10.55	$10.50
Purchase #4	$37.65	6.643%	$40.1511	$40.15	$40.15	$40.20
Purchase #5	$47.88	10.706%	$53.006	$53.01	$53.00	$53.00
Purchase #6	$248.39	12.263%	$278.8501	$278.85	$278.85	$278.90
Purchase #7	$64.70	9.779%	$71.027	$71.03	$71.05	$71.00
7 purchase totals =	$548.34		$598.5745	$598.58	$598.60	$598.60