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	$87.98	7.294%	$94.3973	$94.40	$94.40	$94.40
Purchase #2	$48.25	12.120%	$54.0979	$54.10	$54.10	$54.10
Purchase #3	$207.28	8.493%	$224.8843	$224.88	$224.90	$224.90
Purchase #4	$79.51	12.708%	$89.6141	$89.61	$89.60	$89.60
Purchase #5	$139.72	4.438%	$145.9208	$145.92	$145.90	$145.90
Purchase #6	$157.82	8.291%	$170.9049	$170.90	$170.90	$170.90
Purchase #7	$136.35	4.594%	$142.6139	$142.61	$142.60	$142.60
7 purchase totals =	$856.91		$922.4332	$922.42	$922.40	$922.40