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	$66.32	9.600%	$72.6867	$72.69	$72.70	$72.70
Purchase #2	$69.84	6.178%	$74.1547	$74.15	$74.15	$74.20
Purchase #3	$243.70	10.712%	$269.8051	$269.81	$269.80	$269.80
Purchase #4	$106.97	4.521%	$111.8061	$111.81	$111.80	$111.80
Purchase #5	$59.49	10.105%	$65.5015	$65.50	$65.50	$65.50
Purchase #6	$74.39	13.341%	$84.3144	$84.31	$84.30	$84.30
Purchase #7	$55.43	7.407%	$59.5357	$59.54	$59.55	$59.50
7 purchase totals =	$676.14		$737.8042	$737.81	$737.80	$737.80