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	$137.59	10.247%	$151.6888	$151.69	$151.70	$151.70
Purchase #2	$243.92	12.117%	$273.4758	$273.48	$273.50	$273.50
Purchase #3	$92.72	11.712%	$103.5794	$103.58	$103.60	$103.60
Purchase #4	$107.77	6.371%	$114.636	$114.64	$114.65	$114.60
Purchase #5	$13.88	3.399%	$14.3518	$14.35	$14.35	$14.40
Purchase #6	$27.37	6.179%	$29.0612	$29.06	$29.05	$29.10
Purchase #7	$64.47	7.757%	$69.4709	$69.47	$69.45	$69.50
7 purchase totals =	$687.72		$756.2639	$756.27	$756.30	$756.40