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	$119.74	6.115%	$127.0621	$127.06	$127.05	$127.10
Purchase #2	$169.47	4.852%	$177.6927	$177.69	$177.70	$177.70
Purchase #3	$105.91	7.650%	$114.0121	$114.01	$114.00	$114.00
Purchase #4	$134.40	10.320%	$148.2701	$148.27	$148.25	$148.30
Purchase #5	$39.46	10.639%	$43.6581	$43.66	$43.65	$43.70
Purchase #6	$35.25	6.607%	$37.579	$37.58	$37.60	$37.60
Purchase #7	$11.62	5.386%	$12.2459	$12.25	$12.25	$12.20
7 purchase totals =	$615.85		$660.5200	$660.52	$660.50	$660.60