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	$244.52	4.815%	$256.2936	$256.29	$256.30	$256.30
Purchase #2	$104.66	4.110%	$108.9615	$108.96	$108.95	$109.00
Purchase #3	$48.57	5.132%	$51.0626	$51.06	$51.05	$51.10
Purchase #4	$215.66	4.632%	$225.6494	$225.65	$225.65	$225.60
Purchase #5	$168.58	4.700%	$176.5033	$176.50	$176.50	$176.50
Purchase #6	$146.82	13.517%	$166.6657	$166.67	$166.65	$166.70
Purchase #7	$50.65	6.174%	$53.7771	$53.78	$53.80	$53.80
7 purchase totals =	$979.46		$1,038.9132	$1,038.91	$1,038.90	$1,039.00