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	$235.67	7.381%	$253.0648	$253.06	$253.05	$253.10
Purchase #2	$40.87	3.784%	$42.4165	$42.42	$42.40	$42.40
Purchase #3	$213.28	3.368%	$220.4633	$220.46	$220.45	$220.50
Purchase #4	$51.51	3.501%	$53.3134	$53.31	$53.30	$53.30
Purchase #5	$105.50	4.196%	$109.9268	$109.93	$109.95	$109.90
Purchase #6	$56.65	10.220%	$62.4396	$62.44	$62.45	$62.40
Purchase #7	$238.70	8.314%	$258.5455	$258.55	$258.55	$258.50
7 purchase totals =	$942.18		$1,000.1699	$1,000.17	$1,000.15	$1,000.10