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	$63.25	11.482%	$70.5124	$70.51	$70.50	$70.50
Purchase #2	$153.93	12.647%	$173.3975	$173.40	$173.40	$173.40
Purchase #3	$71.45	10.271%	$78.7886	$78.79	$78.80	$78.80
Purchase #4	$91.73	12.633%	$103.3183	$103.32	$103.30	$103.30
Purchase #5	$52.55	6.407%	$55.9169	$55.92	$55.90	$55.90
Purchase #6	$27.37	13.724%	$31.1263	$31.13	$31.15	$31.10
Purchase #7	$207.30	6.560%	$220.8989	$220.90	$220.90	$220.90
7 purchase totals =	$667.58		$733.9589	$733.97	$733.95	$733.90