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	$115.36	11.481%	$128.6045	$128.60	$128.60	$128.60
Purchase #2	$28.62	10.277%	$31.5613	$31.56	$31.55	$31.60
Purchase #3	$71.80	6.807%	$76.6874	$76.69	$76.70	$76.70
Purchase #4	$121.87	4.615%	$127.4943	$127.49	$127.50	$127.50
Purchase #5	$89.86	12.698%	$101.2704	$101.27	$101.25	$101.30
Purchase #6	$216.65	10.145%	$238.6291	$238.63	$238.65	$238.60
Purchase #7	$141.88	6.756%	$151.4654	$151.47	$151.45	$151.50
7 purchase totals =	$786.04		$855.7124	$855.71	$855.70	$855.80