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	$84.78	13.524%	$96.2456	$96.25	$96.25	$96.20
Purchase #2	$104.41	6.762%	$111.4702	$111.47	$111.45	$111.50
Purchase #3	$166.68	3.837%	$173.0755	$173.08	$173.10	$173.10
Purchase #4	$172.93	5.652%	$182.704	$182.70	$182.70	$182.70
Purchase #5	$235.59	9.648%	$258.3197	$258.32	$258.30	$258.30
Purchase #6	$243.77	9.172%	$266.1286	$266.13	$266.15	$266.10
Purchase #7	$53.80	4.111%	$56.0117	$56.01	$56.00	$56.00
7 purchase totals =	$1,061.96		$1,143.9553	$1,143.96	$1,143.95	$1,143.90