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	$114.87	7.824%	$123.8574	$123.86	$123.85	$123.90
Purchase #2	$196.65	9.621%	$215.5697	$215.57	$215.55	$215.60
Purchase #3	$112.45	8.532%	$122.0442	$122.04	$122.05	$122.00
Purchase #4	$226.80	5.376%	$238.9928	$238.99	$239.00	$239.00
Purchase #5	$135.62	6.146%	$143.9552	$143.96	$143.95	$144.00
Purchase #6	$212.30	4.704%	$222.2866	$222.29	$222.30	$222.30
Purchase #7	$85.61	5.308%	$90.1542	$90.15	$90.15	$90.20
7 purchase totals =	$1,084.30		$1,156.8601	$1,156.86	$1,156.85	$1,157.00