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	$111.61	3.806%	$115.8579	$115.86	$115.85	$115.90
Purchase #2	$63.95	5.691%	$67.5894	$67.59	$67.60	$67.60
Purchase #3	$40.25	7.582%	$43.3018	$43.30	$43.30	$43.30
Purchase #4	$128.81	3.839%	$133.755	$133.76	$133.75	$133.80
Purchase #5	$11.64	6.119%	$12.3523	$12.35	$12.35	$12.40
Purchase #6	$147.40	9.806%	$161.854	$161.85	$161.85	$161.90
Purchase #7	$89.72	4.292%	$93.5708	$93.57	$93.55	$93.60
7 purchase totals =	$593.38		$628.2812	$628.28	$628.25	$628.50