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	$62.67	3.427%	$64.8177	$64.82	$64.80	$64.80
Purchase #2	$8.40	3.379%	$8.6838	$8.68	$8.70	$8.70
Purchase #3	$165.98	4.126%	$172.8283	$172.83	$172.85	$172.80
Purchase #4	$44.88	12.760%	$50.6067	$50.61	$50.60	$50.60
Purchase #5	$41.78	5.183%	$43.9455	$43.95	$43.95	$43.90
Purchase #6	$80.54	11.315%	$89.6531	$89.65	$89.65	$89.70
Purchase #7	$136.49	13.308%	$154.6541	$154.65	$154.65	$154.70
7 purchase totals =	$540.74		$585.1892	$585.19	$585.20	$585.20