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	$227.38	10.559%	$251.3891	$251.39	$251.40	$251.40
Purchase #2	$47.98	6.704%	$51.1966	$51.20	$51.20	$51.20
Purchase #3	$48.33	10.546%	$53.4269	$53.43	$53.45	$53.40
Purchase #4	$134.68	5.499%	$142.0861	$142.09	$142.10	$142.10
Purchase #5	$204.25	9.287%	$223.2187	$223.22	$223.20	$223.20
Purchase #6	$111.40	3.328%	$115.1074	$115.11	$115.10	$115.10
Purchase #7	$159.37	12.614%	$179.4729	$179.47	$179.45	$179.50
7 purchase totals =	$933.39		$1,015.8977	$1,015.91	$1,015.90	$1,015.90