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	$113.92	12.285%	$127.9151	$127.92	$127.90	$127.90
Purchase #2	$14.98	6.203%	$15.9092	$15.91	$15.90	$15.90
Purchase #3	$162.37	9.781%	$178.2514	$178.25	$178.25	$178.30
Purchase #4	$19.26	4.727%	$20.1704	$20.17	$20.15	$20.20
Purchase #5	$57.77	5.721%	$61.075	$61.08	$61.10	$61.10
Purchase #6	$233.73	11.105%	$259.6857	$259.69	$259.70	$259.70
Purchase #7	$101.80	10.270%	$112.2549	$112.25	$112.25	$112.30
7 purchase totals =	$703.83		$775.2617	$775.27	$775.25	$775.40