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	$179.43	11.559%	$200.1703	$200.17	$200.15	$200.20
Purchase #2	$125.92	6.472%	$134.0695	$134.07	$134.05	$134.10
Purchase #3	$86.28	5.827%	$91.3075	$91.31	$91.30	$91.30
Purchase #4	$124.89	5.429%	$131.6703	$131.67	$131.65	$131.70
Purchase #5	$148.90	5.481%	$157.0612	$157.06	$157.05	$157.10
Purchase #6	$98.76	13.669%	$112.2595	$112.26	$112.25	$112.30
Purchase #7	$211.60	3.271%	$218.5214	$218.52	$218.50	$218.50
7 purchase totals =	$975.78		$1,045.0597	$1,045.06	$1,044.95	$1,045.20