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	$240.77	6.832%	$257.2194	$257.22	$257.20	$257.20
Purchase #2	$115.37	10.813%	$127.845	$127.85	$127.85	$127.80
Purchase #3	$171.65	13.835%	$195.3978	$195.40	$195.40	$195.40
Purchase #4	$49.74	6.440%	$52.9433	$52.94	$52.95	$52.90
Purchase #5	$139.63	13.516%	$158.5024	$158.50	$158.50	$158.50
Purchase #6	$182.72	12.478%	$205.5198	$205.52	$205.50	$205.50
Purchase #7	$155.74	7.337%	$167.1666	$167.17	$167.15	$167.20
7 purchase totals =	$1,055.62		$1,164.5943	$1,164.60	$1,164.55	$1,164.50