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	$110.95	11.795%	$124.0366	$124.04	$124.05	$124.00
Purchase #2	$99.98	12.630%	$112.6075	$112.61	$112.60	$112.60
Purchase #3	$119.55	3.573%	$123.8215	$123.82	$123.80	$123.80
Purchase #4	$110.63	3.538%	$114.5441	$114.54	$114.55	$114.50
Purchase #5	$57.59	8.630%	$62.56	$62.56	$62.55	$62.60
Purchase #6	$148.67	6.527%	$158.3737	$158.37	$158.35	$158.40
Purchase #7	$226.25	13.643%	$257.1173	$257.12	$257.10	$257.10
7 purchase totals =	$873.62		$953.0607	$953.06	$953.00	$953.00