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	$13.59	7.303%	$14.5825	$14.58	$14.60	$14.60
Purchase #2	$80.74	3.537%	$83.5958	$83.60	$83.60	$83.60
Purchase #3	$62.72	13.174%	$70.9827	$70.98	$71.00	$71.00
Purchase #4	$156.73	10.859%	$173.7493	$173.75	$173.75	$173.70
Purchase #5	$39.76	3.212%	$41.0371	$41.04	$41.05	$41.00
Purchase #6	$53.48	6.310%	$56.8546	$56.85	$56.85	$56.90
Purchase #7	$127.76	3.296%	$131.971	$131.97	$131.95	$132.00
7 purchase totals =	$534.78		$572.7730	$572.77	$572.80	$572.80