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	$58.38	11.639%	$65.1748	$65.17	$65.15	$65.20
Purchase #2	$42.34	6.548%	$45.1124	$45.11	$45.10	$45.10
Purchase #3	$172.61	11.111%	$191.7887	$191.79	$191.80	$191.80
Purchase #4	$176.42	11.237%	$196.2443	$196.24	$196.25	$196.20
Purchase #5	$123.33	9.277%	$134.7713	$134.77	$134.75	$134.80
Purchase #6	$38.65	10.496%	$42.7067	$42.71	$42.70	$42.70
Purchase #7	$38.71	9.315%	$42.3158	$42.32	$42.30	$42.30
7 purchase totals =	$650.44		$718.1140	$718.11	$718.05	$718.10