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	$117.96	4.367%	$123.1113	$123.11	$123.10	$123.10
Purchase #2	$164.44	13.439%	$186.5391	$186.54	$186.55	$186.50
Purchase #3	$166.70	6.111%	$176.887	$176.89	$176.90	$176.90
Purchase #4	$94.54	13.356%	$107.1668	$107.17	$107.15	$107.20
Purchase #5	$146.26	5.634%	$154.5003	$154.50	$154.50	$154.50
Purchase #6	$101.44	9.814%	$111.3953	$111.40	$111.40	$111.40
Purchase #7	$241.38	9.226%	$263.6497	$263.65	$263.65	$263.60
7 purchase totals =	$1,032.72		$1,123.2495	$1,123.26	$1,123.25	$1,123.20