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	$238.98	6.645%	$254.8602	$254.86	$254.85	$254.90
Purchase #2	$101.43	5.506%	$107.0147	$107.01	$107.00	$107.00
Purchase #3	$54.25	4.473%	$56.6766	$56.68	$56.70	$56.70
Purchase #4	$18.62	9.626%	$20.4124	$20.41	$20.40	$20.40
Purchase #5	$87.35	10.248%	$96.3016	$96.30	$96.30	$96.30
Purchase #6	$233.98	3.349%	$241.816	$241.82	$241.80	$241.80
Purchase #7	$200.68	12.509%	$225.7831	$225.78	$225.80	$225.80
7 purchase totals =	$935.29		$1,002.8646	$1,002.86	$1,002.85	$1,002.90