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	$186.54	13.293%	$211.3368	$211.34	$211.35	$211.30
Purchase #2	$72.25	6.267%	$76.7779	$76.78	$76.80	$76.80
Purchase #3	$154.89	11.823%	$173.2026	$173.20	$173.20	$173.20
Purchase #4	$246.35	3.624%	$255.2777	$255.28	$255.30	$255.30
Purchase #5	$45.45	13.493%	$51.5826	$51.58	$51.60	$51.60
Purchase #6	$182.84	7.537%	$196.6207	$196.62	$196.60	$196.60
Purchase #7	$168.30	6.104%	$178.573	$178.57	$178.55	$178.60
7 purchase totals =	$1,056.62		$1,143.3713	$1,143.37	$1,143.40	$1,143.40