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	$215.54	9.105%	$235.1649	$235.16	$235.15	$235.20
Purchase #2	$132.90	7.407%	$142.7439	$142.74	$142.75	$142.70
Purchase #3	$117.95	11.351%	$131.3385	$131.34	$131.35	$131.30
Purchase #4	$148.49	7.748%	$159.995	$160.00	$160.00	$160.00
Purchase #5	$207.56	6.216%	$220.4619	$220.46	$220.45	$220.50
Purchase #6	$56.93	3.781%	$59.0825	$59.08	$59.10	$59.10
Purchase #7	$59.83	4.260%	$62.3788	$62.38	$62.40	$62.40
7 purchase totals =	$939.20		$1,011.1655	$1,011.16	$1,011.20	$1,011.20