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	$9.92	10.307%	$10.9425	$10.94	$10.95	$10.90
Purchase #2	$18.42	11.835%	$20.6	$20.60	$20.60	$20.60
Purchase #3	$77.25	4.494%	$80.7216	$80.72	$80.70	$80.70
Purchase #4	$162.98	5.627%	$172.1509	$172.15	$172.15	$172.20
Purchase #5	$55.60	3.676%	$57.6439	$57.64	$57.65	$57.60
Purchase #6	$196.46	9.717%	$215.55	$215.55	$215.55	$215.60
Purchase #7	$29.63	6.266%	$31.4866	$31.49	$31.50	$31.50
7 purchase totals =	$550.26		$589.0955	$589.09	$589.10	$589.10