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	$161.45	12.291%	$181.2938	$181.29	$181.30	$181.30
Purchase #2	$40.63	3.688%	$42.1284	$42.13	$42.15	$42.10
Purchase #3	$177.53	3.615%	$183.9477	$183.95	$183.95	$183.90
Purchase #4	$198.75	12.458%	$223.5103	$223.51	$223.50	$223.50
Purchase #5	$48.78	6.365%	$51.8848	$51.88	$51.90	$51.90
Purchase #6	$235.80	3.215%	$243.381	$243.38	$243.40	$243.40
Purchase #7	$132.96	3.671%	$137.841	$137.84	$137.85	$137.80
7 purchase totals =	$995.90		$1,063.9870	$1,063.98	$1,064.05	$1,063.90