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	$140.30	8.212%	$151.8214	$151.82	$151.80	$151.80
Purchase #2	$162.28	8.235%	$175.6438	$175.64	$175.65	$175.60
Purchase #3	$106.76	4.532%	$111.5984	$111.60	$111.60	$111.60
Purchase #4	$118.59	3.631%	$122.896	$122.90	$122.90	$122.90
Purchase #5	$61.29	5.555%	$64.6947	$64.69	$64.70	$64.70
Purchase #6	$169.67	6.126%	$180.064	$180.06	$180.05	$180.10
Purchase #7	$100.86	10.839%	$111.7922	$111.79	$111.80	$111.80
7 purchase totals =	$859.75		$918.5105	$918.50	$918.50	$918.50