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	$44.63	4.431%	$46.6076	$46.61	$46.60	$46.60
Purchase #2	$248.55	6.705%	$265.2153	$265.22	$265.20	$265.20
Purchase #3	$226.40	9.704%	$248.3699	$248.37	$248.35	$248.40
Purchase #4	$40.83	3.196%	$42.1349	$42.13	$42.15	$42.10
Purchase #5	$110.32	3.681%	$114.3809	$114.38	$114.40	$114.40
Purchase #6	$16.53	12.488%	$18.5943	$18.59	$18.60	$18.60
Purchase #7	$187.98	5.609%	$198.5238	$198.52	$198.50	$198.50
7 purchase totals =	$875.24		$933.8267	$933.82	$933.80	$933.80