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	$233.32	3.648%	$241.8315	$241.83	$241.85	$241.80
Purchase #2	$47.37	9.679%	$51.9549	$51.95	$51.95	$52.00
Purchase #3	$123.76	10.213%	$136.3996	$136.40	$136.40	$136.40
Purchase #4	$11.42	8.296%	$12.3674	$12.37	$12.35	$12.40
Purchase #5	$249.73	13.779%	$284.1403	$284.14	$284.15	$284.10
Purchase #6	$241.57	6.830%	$258.0692	$258.07	$258.05	$258.10
Purchase #7	$151.81	3.232%	$156.7165	$156.72	$156.70	$156.70
7 purchase totals =	$1,058.98		$1,141.4794	$1,141.48	$1,141.45	$1,141.50