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	$30.37	6.644%	$32.3878	$32.39	$32.40	$32.40
Purchase #2	$77.69	11.857%	$86.9017	$86.90	$86.90	$86.90
Purchase #3	$91.80	3.263%	$94.7954	$94.80	$94.80	$94.80
Purchase #4	$180.31	11.658%	$201.3305	$201.33	$201.35	$201.30
Purchase #5	$172.78	8.262%	$187.0551	$187.06	$187.05	$187.10
Purchase #6	$210.57	7.160%	$225.6468	$225.65	$225.65	$225.60
Purchase #7	$248.55	9.381%	$271.8665	$271.87	$271.85	$271.90
7 purchase totals =	$1,012.07		$1,099.9838	$1,100.00	$1,100.00	$1,100.00