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	$113.94	8.361%	$123.4665	$123.47	$123.45	$123.50
Purchase #2	$125.78	10.819%	$139.3881	$139.39	$139.40	$139.40
Purchase #3	$125.27	4.784%	$131.2629	$131.26	$131.25	$131.30
Purchase #4	$16.47	9.723%	$18.0714	$18.07	$18.05	$18.10
Purchase #5	$106.90	11.450%	$119.1401	$119.14	$119.15	$119.10
Purchase #6	$56.52	10.221%	$62.2969	$62.30	$62.30	$62.30
Purchase #7	$54.61	5.204%	$57.4519	$57.45	$57.45	$57.50
7 purchase totals =	$599.49		$651.0778	$651.08	$651.05	$651.20