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	$110.63	11.677%	$123.5483	$123.55	$123.55	$123.50
Purchase #2	$153.80	9.646%	$168.6355	$168.64	$168.65	$168.60
Purchase #3	$221.30	13.449%	$251.0626	$251.06	$251.05	$251.10
Purchase #4	$109.25	12.724%	$123.151	$123.15	$123.15	$123.20
Purchase #5	$205.55	9.370%	$224.81	$224.81	$224.80	$224.80
Purchase #6	$107.74	3.233%	$111.2232	$111.22	$111.20	$111.20
Purchase #7	$123.95	3.351%	$128.1036	$128.10	$128.10	$128.10
7 purchase totals =	$1,032.22		$1,130.5342	$1,130.53	$1,130.50	$1,130.50