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	$130.39	9.771%	$143.1304	$143.13	$143.15	$143.10
Purchase #2	$138.31	11.385%	$154.0566	$154.06	$154.05	$154.10
Purchase #3	$230.82	3.336%	$238.5202	$238.52	$238.50	$238.50
Purchase #4	$139.66	11.281%	$155.415	$155.42	$155.40	$155.40
Purchase #5	$170.75	11.696%	$190.7209	$190.72	$190.70	$190.70
Purchase #6	$202.77	9.794%	$222.6293	$222.63	$222.65	$222.60
Purchase #7	$193.57	8.249%	$209.5376	$209.54	$209.55	$209.50
7 purchase totals =	$1,206.27		$1,314.0100	$1,314.02	$1,314.00	$1,313.90