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	$88.59	7.565%	$95.2918	$95.29	$95.30	$95.30
Purchase #2	$209.63	8.701%	$227.8699	$227.87	$227.85	$227.90
Purchase #3	$38.92	5.553%	$41.0812	$41.08	$41.10	$41.10
Purchase #4	$76.30	9.870%	$83.8308	$83.83	$83.85	$83.80
Purchase #5	$78.78	12.486%	$88.6165	$88.62	$88.60	$88.60
Purchase #6	$40.65	13.743%	$46.2365	$46.24	$46.25	$46.20
Purchase #7	$215.65	10.151%	$237.5406	$237.54	$237.55	$237.50
7 purchase totals =	$748.52		$820.4673	$820.47	$820.50	$820.40