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	$54.70	4.456%	$57.1374	$57.14	$57.15	$57.10
Purchase #2	$145.56	10.205%	$160.4144	$160.41	$160.40	$160.40
Purchase #3	$67.36	7.276%	$72.2611	$72.26	$72.25	$72.30
Purchase #4	$49.45	6.223%	$52.5273	$52.53	$52.55	$52.50
Purchase #5	$50.53	11.509%	$56.3455	$56.35	$56.35	$56.30
Purchase #6	$81.58	12.394%	$91.691	$91.69	$91.70	$91.70
Purchase #7	$75.30	4.105%	$78.3911	$78.39	$78.40	$78.40
7 purchase totals =	$524.48		$568.7678	$568.77	$568.80	$568.70