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	$102.85	12.383%	$115.5859	$115.59	$115.60	$115.60
Purchase #2	$203.97	8.872%	$222.0662	$222.07	$222.05	$222.10
Purchase #3	$74.35	9.793%	$81.6311	$81.63	$81.65	$81.60
Purchase #4	$226.43	7.237%	$242.8167	$242.82	$242.80	$242.80
Purchase #5	$47.29	4.846%	$49.5817	$49.58	$49.60	$49.60
Purchase #6	$106.83	4.801%	$111.9589	$111.96	$111.95	$112.00
Purchase #7	$213.87	11.368%	$238.1827	$238.18	$238.20	$238.20
7 purchase totals =	$975.59		$1,061.8232	$1,061.83	$1,061.85	$1,061.90