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	$72.38	8.409%	$78.4664	$78.47	$78.45	$78.50
Purchase #2	$190.90	5.245%	$200.9127	$200.91	$200.90	$200.90
Purchase #3	$180.67	9.631%	$198.0703	$198.07	$198.05	$198.10
Purchase #4	$159.46	10.697%	$176.5174	$176.52	$176.50	$176.50
Purchase #5	$131.35	8.157%	$142.0642	$142.06	$142.05	$142.10
Purchase #6	$222.33	5.159%	$233.8	$233.80	$233.80	$233.80
Purchase #7	$72.36	3.223%	$74.6922	$74.69	$74.70	$74.70
7 purchase totals =	$1,029.45		$1,104.5232	$1,104.52	$1,104.45	$1,104.60