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	$16.88	3.471%	$17.4659	$17.47	$17.45	$17.50
Purchase #2	$191.32	10.768%	$211.9213	$211.92	$211.90	$211.90
Purchase #3	$45.62	8.804%	$49.6364	$49.64	$49.65	$49.60
Purchase #4	$179.65	3.104%	$185.2263	$185.23	$185.25	$185.20
Purchase #5	$205.65	8.473%	$223.0747	$223.07	$223.05	$223.10
Purchase #6	$236.60	13.407%	$268.321	$268.32	$268.30	$268.30
Purchase #7	$57.79	4.860%	$60.5986	$60.60	$60.60	$60.60
7 purchase totals =	$933.51		$1,016.2442	$1,016.25	$1,016.20	$1,016.20