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	$140.50	12.831%	$158.5276	$158.53	$158.55	$158.50
Purchase #2	$97.61	8.363%	$105.7731	$105.77	$105.75	$105.80
Purchase #3	$137.46	6.848%	$146.8733	$146.87	$146.85	$146.90
Purchase #4	$112.66	9.444%	$123.2996	$123.30	$123.30	$123.30
Purchase #5	$246.55	6.595%	$262.81	$262.81	$262.80	$262.80
Purchase #6	$155.74	12.281%	$174.8664	$174.87	$174.85	$174.90
Purchase #7	$105.38	9.861%	$115.7715	$115.77	$115.75	$115.80
7 purchase totals =	$995.90		$1,087.9215	$1,087.92	$1,087.85	$1,088.00