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	$145.35	6.859%	$155.3196	$155.32	$155.30	$155.30
Purchase #2	$109.82	4.533%	$114.7981	$114.80	$114.80	$114.80
Purchase #3	$104.37	7.826%	$112.538	$112.54	$112.55	$112.50
Purchase #4	$49.25	8.839%	$53.6032	$53.60	$53.60	$53.60
Purchase #5	$153.56	3.147%	$158.3925	$158.39	$158.40	$158.40
Purchase #6	$187.39	4.821%	$196.4241	$196.42	$196.40	$196.40
Purchase #7	$64.51	12.511%	$72.5808	$72.58	$72.60	$72.60
7 purchase totals =	$814.25		$863.6563	$863.65	$863.65	$863.60