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	$42.73	4.716%	$44.7451	$44.75	$44.75	$44.70
Purchase #2	$118.87	6.669%	$126.7974	$126.80	$126.80	$126.80
Purchase #3	$146.89	7.728%	$158.2417	$158.24	$158.25	$158.20
Purchase #4	$40.88	4.187%	$42.5916	$42.59	$42.60	$42.60
Purchase #5	$187.27	13.129%	$211.8567	$211.86	$211.85	$211.90
Purchase #6	$94.56	10.870%	$104.8387	$104.84	$104.85	$104.80
Purchase #7	$214.78	5.140%	$225.8197	$225.82	$225.80	$225.80
7 purchase totals =	$845.98		$914.8909	$914.90	$914.90	$914.80