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	$148.79	5.834%	$157.4704	$157.47	$157.45	$157.50
Purchase #2	$8.37	5.201%	$8.8053	$8.81	$8.80	$8.80
Purchase #3	$100.33	5.426%	$105.7739	$105.77	$105.75	$105.80
Purchase #4	$105.43	5.865%	$111.6135	$111.61	$111.60	$111.60
Purchase #5	$39.86	9.764%	$43.7519	$43.75	$43.75	$43.80
Purchase #6	$204.85	8.798%	$222.8727	$222.87	$222.85	$222.90
Purchase #7	$117.63	7.539%	$126.4981	$126.50	$126.50	$126.50
7 purchase totals =	$725.26		$776.7858	$776.78	$776.70	$776.90