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	$115.57	10.547%	$127.7592	$127.76	$127.75	$127.80
Purchase #2	$208.54	3.162%	$215.134	$215.13	$215.15	$215.10
Purchase #3	$152.29	9.391%	$166.5916	$166.59	$166.60	$166.60
Purchase #4	$167.52	4.428%	$174.9378	$174.94	$174.95	$174.90
Purchase #5	$89.58	5.357%	$94.3788	$94.38	$94.40	$94.40
Purchase #6	$81.31	5.565%	$85.8349	$85.83	$85.85	$85.80
Purchase #7	$41.52	5.356%	$43.7438	$43.74	$43.75	$43.70
7 purchase totals =	$856.33		$908.3801	$908.37	$908.45	$908.30