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	$67.38	13.616%	$76.5545	$76.55	$76.55	$76.60
Purchase #2	$115.63	10.256%	$127.489	$127.49	$127.50	$127.50
Purchase #3	$120.61	9.801%	$132.431	$132.43	$132.45	$132.40
Purchase #4	$77.92	13.262%	$88.2538	$88.25	$88.25	$88.30
Purchase #5	$155.83	7.146%	$166.9656	$166.97	$166.95	$167.00
Purchase #6	$236.41	3.396%	$244.4385	$244.44	$244.45	$244.40
Purchase #7	$212.77	12.294%	$238.9279	$238.93	$238.95	$238.90
7 purchase totals =	$986.55		$1,075.0603	$1,075.06	$1,075.10	$1,075.10