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	$147.88	11.294%	$164.5816	$164.58	$164.60	$164.60
Purchase #2	$46.66	10.559%	$51.5868	$51.59	$51.60	$51.60
Purchase #3	$208.63	3.493%	$215.9174	$215.92	$215.90	$215.90
Purchase #4	$149.46	6.112%	$158.595	$158.60	$158.60	$158.60
Purchase #5	$221.94	4.285%	$231.4501	$231.45	$231.45	$231.50
Purchase #6	$67.71	4.541%	$70.7847	$70.78	$70.80	$70.80
Purchase #7	$233.70	10.472%	$258.1731	$258.17	$258.15	$258.20
7 purchase totals =	$1,075.98		$1,151.0887	$1,151.09	$1,151.10	$1,151.20