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	$167.46	7.137%	$179.4116	$179.41	$179.40	$179.40
Purchase #2	$20.70	3.403%	$21.4044	$21.40	$21.40	$21.40
Purchase #3	$150.43	7.151%	$161.1872	$161.19	$161.20	$161.20
Purchase #4	$34.91	7.573%	$37.5537	$37.55	$37.55	$37.60
Purchase #5	$178.78	9.839%	$196.3702	$196.37	$196.35	$196.40
Purchase #6	$107.50	11.305%	$119.6529	$119.65	$119.65	$119.70
Purchase #7	$25.63	11.648%	$28.6154	$28.62	$28.60	$28.60
7 purchase totals =	$685.41		$744.1954	$744.19	$744.15	$744.30