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	$212.88	7.857%	$229.606	$229.61	$229.60	$229.60
Purchase #2	$88.94	6.169%	$94.4267	$94.43	$94.45	$94.40
Purchase #3	$38.95	8.170%	$42.1322	$42.13	$42.15	$42.10
Purchase #4	$90.83	13.721%	$103.2928	$103.29	$103.30	$103.30
Purchase #5	$142.44	9.481%	$155.9447	$155.94	$155.95	$155.90
Purchase #6	$197.78	3.179%	$204.0674	$204.07	$204.05	$204.10
Purchase #7	$14.52	9.421%	$15.8879	$15.89	$15.90	$15.90
7 purchase totals =	$786.34		$845.3577	$845.36	$845.40	$845.30