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	$165.52	12.681%	$186.5096	$186.51	$186.50	$186.50
Purchase #2	$13.27	3.666%	$13.7565	$13.76	$13.75	$13.80
Purchase #3	$66.97	7.195%	$71.7885	$71.79	$71.80	$71.80
Purchase #4	$101.61	9.742%	$111.5088	$111.51	$111.50	$111.50
Purchase #5	$45.75	5.478%	$48.2562	$48.26	$48.25	$48.30
Purchase #6	$48.87	6.143%	$51.8721	$51.87	$51.85	$51.90
Purchase #7	$204.84	4.222%	$213.4883	$213.49	$213.50	$213.50
7 purchase totals =	$646.83		$697.1800	$697.19	$697.15	$697.30