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	$41.58	5.715%	$43.9563	$43.96	$43.95	$44.00
Purchase #2	$239.82	12.500%	$269.7975	$269.80	$269.80	$269.80
Purchase #3	$92.33	4.563%	$96.543	$96.54	$96.55	$96.50
Purchase #4	$79.49	4.177%	$82.8103	$82.81	$82.80	$82.80
Purchase #5	$229.50	11.852%	$256.7003	$256.70	$256.70	$256.70
Purchase #6	$38.32	6.400%	$40.7725	$40.77	$40.75	$40.80
Purchase #7	$106.96	10.864%	$118.5801	$118.58	$118.60	$118.60
7 purchase totals =	$828.00		$909.1600	$909.16	$909.15	$909.20