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	$117.50	5.380%	$123.8215	$123.82	$123.80	$123.80
Purchase #2	$139.65	13.345%	$158.2863	$158.29	$158.30	$158.30
Purchase #3	$94.94	11.790%	$106.1334	$106.13	$106.15	$106.10
Purchase #4	$242.63	4.829%	$254.3466	$254.35	$254.35	$254.30
Purchase #5	$146.68	12.806%	$165.4638	$165.46	$165.45	$165.50
Purchase #6	$200.28	5.649%	$211.5938	$211.59	$211.60	$211.60
Purchase #7	$63.29	6.481%	$67.3918	$67.39	$67.40	$67.40
7 purchase totals =	$1,004.97		$1,087.0372	$1,087.03	$1,087.05	$1,087.00