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	$212.56	12.274%	$238.6496	$238.65	$238.65	$238.60
Purchase #2	$210.76	13.162%	$238.5002	$238.50	$238.50	$238.50
Purchase #3	$121.47	5.783%	$128.4946	$128.49	$128.50	$128.50
Purchase #4	$98.85	3.733%	$102.5401	$102.54	$102.55	$102.50
Purchase #5	$177.31	10.760%	$196.3886	$196.39	$196.40	$196.40
Purchase #6	$204.43	3.242%	$211.0576	$211.06	$211.05	$211.10
Purchase #7	$26.54	6.586%	$28.2879	$28.29	$28.30	$28.30
7 purchase totals =	$1,051.92		$1,143.9186	$1,143.92	$1,143.95	$1,143.90