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	$107.43	11.481%	$119.764	$119.76	$119.75	$119.80
Purchase #2	$187.42	6.152%	$198.9501	$198.95	$198.95	$199.00
Purchase #3	$180.61	5.723%	$190.9463	$190.95	$190.95	$190.90
Purchase #4	$56.30	9.158%	$61.456	$61.46	$61.45	$61.50
Purchase #5	$109.42	7.728%	$117.876	$117.88	$117.90	$117.90
Purchase #6	$153.59	3.820%	$159.4571	$159.46	$159.45	$159.50
Purchase #7	$67.79	4.325%	$70.7219	$70.72	$70.70	$70.70
7 purchase totals =	$862.56		$919.1714	$919.18	$919.15	$919.30