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	$167.59	10.647%	$185.4333	$185.43	$185.45	$185.40
Purchase #2	$57.60	12.359%	$64.7188	$64.72	$64.70	$64.70
Purchase #3	$84.35	6.301%	$89.6649	$89.66	$89.65	$89.70
Purchase #4	$135.46	7.831%	$146.0679	$146.07	$146.05	$146.10
Purchase #5	$250.94	3.859%	$260.6238	$260.62	$260.60	$260.60
Purchase #6	$79.89	9.695%	$87.6353	$87.64	$87.65	$87.60
Purchase #7	$206.45	4.422%	$215.5792	$215.58	$215.60	$215.60
7 purchase totals =	$982.28		$1,049.7232	$1,049.72	$1,049.70	$1,049.70