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	$49.61	7.848%	$53.5034	$53.50	$53.50	$53.50
Purchase #2	$103.31	7.856%	$111.426	$111.43	$111.45	$111.40
Purchase #3	$56.31	3.872%	$58.4903	$58.49	$58.50	$58.50
Purchase #4	$133.96	8.171%	$144.9059	$144.91	$144.90	$144.90
Purchase #5	$136.88	4.530%	$143.0807	$143.08	$143.10	$143.10
Purchase #6	$46.97	3.119%	$48.435	$48.44	$48.45	$48.40
Purchase #7	$249.80	13.107%	$282.5413	$282.54	$282.55	$282.50
7 purchase totals =	$776.84		$842.3826	$842.39	$842.45	$842.30