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	$228.27	3.450%	$236.1453	$236.15	$236.15	$236.10
Purchase #2	$208.60	12.705%	$235.1026	$235.10	$235.10	$235.10
Purchase #3	$67.83	12.474%	$76.2911	$76.29	$76.30	$76.30
Purchase #4	$40.49	6.397%	$43.0801	$43.08	$43.10	$43.10
Purchase #5	$91.54	11.665%	$102.2181	$102.22	$102.20	$102.20
Purchase #6	$90.52	4.509%	$94.6015	$94.60	$94.60	$94.60
Purchase #7	$104.60	6.535%	$111.4356	$111.44	$111.45	$111.40
7 purchase totals =	$831.85		$898.8743	$898.88	$898.90	$898.80