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	$103.49	10.471%	$114.3264	$114.33	$114.35	$114.30
Purchase #2	$207.47	9.647%	$227.4846	$227.48	$227.50	$227.50
Purchase #3	$72.49	9.190%	$79.1518	$79.15	$79.15	$79.20
Purchase #4	$103.91	7.852%	$112.069	$112.07	$112.05	$112.10
Purchase #5	$127.46	13.352%	$144.4785	$144.48	$144.50	$144.50
Purchase #6	$75.29	4.377%	$78.5854	$78.59	$78.60	$78.60
Purchase #7	$162.26	7.537%	$174.4895	$174.49	$174.50	$174.50
7 purchase totals =	$852.37		$930.5852	$930.59	$930.65	$930.70