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	$148.32	13.790%	$168.7733	$168.77	$168.75	$168.80
Purchase #2	$102.96	5.531%	$108.6547	$108.65	$108.65	$108.70
Purchase #3	$185.79	12.687%	$209.3612	$209.36	$209.35	$209.40
Purchase #4	$161.52	9.183%	$176.3524	$176.35	$176.35	$176.40
Purchase #5	$200.78	5.128%	$211.076	$211.08	$211.10	$211.10
Purchase #6	$38.29	6.490%	$40.775	$40.78	$40.80	$40.80
Purchase #7	$91.74	13.866%	$104.4607	$104.46	$104.45	$104.50
7 purchase totals =	$929.40		$1,019.4533	$1,019.45	$1,019.45	$1,019.70