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	$201.67	9.817%	$221.4679	$221.47	$221.45	$221.50
Purchase #2	$143.84	6.537%	$153.2428	$153.24	$153.25	$153.20
Purchase #3	$114.53	7.651%	$123.2927	$123.29	$123.30	$123.30
Purchase #4	$73.38	10.588%	$81.1495	$81.15	$81.15	$81.10
Purchase #5	$224.87	3.644%	$233.0643	$233.06	$233.05	$233.10
Purchase #6	$79.57	13.139%	$90.0247	$90.02	$90.00	$90.00
Purchase #7	$145.85	8.703%	$158.5433	$158.54	$158.55	$158.50
7 purchase totals =	$983.71		$1,060.7852	$1,060.77	$1,060.75	$1,060.70