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	$208.64	13.193%	$236.1659	$236.17	$236.15	$236.20
Purchase #2	$104.80	9.373%	$114.6229	$114.62	$114.60	$114.60
Purchase #3	$191.86	10.426%	$211.8633	$211.86	$211.85	$211.90
Purchase #4	$112.30	13.743%	$127.7334	$127.73	$127.75	$127.70
Purchase #5	$136.55	11.806%	$152.6711	$152.67	$152.65	$152.70
Purchase #6	$120.95	11.183%	$134.4758	$134.48	$134.50	$134.50
Purchase #7	$51.42	6.525%	$54.7752	$54.78	$54.80	$54.80
7 purchase totals =	$926.52		$1,032.3076	$1,032.31	$1,032.30	$1,032.40