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	$67.96	12.614%	$76.5325	$76.53	$76.55	$76.50
Purchase #2	$160.77	3.117%	$165.7812	$165.78	$165.80	$165.80
Purchase #3	$224.47	12.540%	$252.6185	$252.62	$252.60	$252.60
Purchase #4	$223.69	5.196%	$235.3129	$235.31	$235.30	$235.30
Purchase #5	$53.54	3.728%	$55.536	$55.54	$55.55	$55.50
Purchase #6	$230.94	6.113%	$245.0574	$245.06	$245.05	$245.10
Purchase #7	$208.60	7.643%	$224.5433	$224.54	$224.55	$224.50
7 purchase totals =	$1,169.97		$1,255.3818	$1,255.38	$1,255.40	$1,255.30