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	$224.87	4.563%	$235.1308	$235.13	$235.15	$235.10
Purchase #2	$60.46	7.326%	$64.8893	$64.89	$64.90	$64.90
Purchase #3	$236.95	7.204%	$254.0199	$254.02	$254.00	$254.00
Purchase #4	$45.33	7.188%	$48.5883	$48.59	$48.60	$48.60
Purchase #5	$186.32	5.705%	$196.9496	$196.95	$196.95	$196.90
Purchase #6	$236.51	10.801%	$262.0554	$262.06	$262.05	$262.10
Purchase #7	$212.71	4.873%	$223.0754	$223.08	$223.10	$223.10
7 purchase totals =	$1,203.15		$1,284.7087	$1,284.72	$1,284.75	$1,284.70