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	$211.94	4.425%	$221.3183	$221.32	$221.30	$221.30
Purchase #2	$118.26	4.745%	$123.8714	$123.87	$123.85	$123.90
Purchase #3	$191.90	10.701%	$212.4352	$212.44	$212.45	$212.40
Purchase #4	$192.83	6.697%	$205.7438	$205.74	$205.75	$205.70
Purchase #5	$38.51	11.806%	$43.0565	$43.06	$43.05	$43.10
Purchase #6	$38.51	11.314%	$42.867	$42.87	$42.85	$42.90
Purchase #7	$19.38	8.743%	$21.0744	$21.07	$21.05	$21.10
7 purchase totals =	$811.33		$870.3666	$870.37	$870.30	$870.40